I would suggest -doing- something about it as a long term investment and deeper study in place of or as part of your aikido training, instead of continuing to just pick up pieces here and there.
The things being discussed are very, very basic structure issues and are really just a small part of that picture with all sorts of potential errors when considering them independently. I for one would never agree to a tuck in any form. In fact for most, with their musculature like it is, it does as much harm as benefit for support as they will just tighten into a tuck. A better idea is to think of stretching and opening the spine and let the sacrum drop. In fact I could make a case for certain things to do with the crotch or deep groin area (no jokes please) that would make the sacrum look like it wasn't tucking but was flat or even tilting a bit back instead!. I have some friends-one who teaches Yang Taiji and another who practices it who keep arguing with me but since they can't throw me- we agree to disagree. IMO, tucking leads to other vulnerabilities that can be eliminated with a freedom in the crotch and hips.
More importantly-neither of which has anything to do with aiki.
Building your frame, strengthening your tendons, and engaging and using the fascial system as a unit with the breath are all part of making a bujutsu or martial body. As that body is tempered and built more slack is removed. Let's call "slack" here- various means and methods whereby the normal body moves in pieces and parts, and its weight is all over the place when it does. You may note that some older teachers have a range of motion where they move just so far and their movement effects you. The reason is their structure is more developed, some of them really don't have clue how to replicate it and teach it to others. They did it themselves through kata while their peers stunk up the place. But kata has always been a gamble as a learning tool or model. From what I have seen even then some of the guys I have played with have holes in their game-all over the place.
It's not that way with someone training their body. There are specific things you can do. As you build it (with movement with intent, so in movement you remove weaknesses) and your intent becomes increasingly profound, you remove more and more slack. Your range of motion, BEFORE you start affecting your opponent, becomes less and less, finally to the point that almost even thinking about moving affects them. I have had people tell me so and so teacher feel this way only to find out. "No, no they don't." And when you show them they agree it's not the same.
So, there are ways to knit your body together; some hard some soft. As George knows from back in the aikido list days I have been telling aikido people they are too strong and muscular and do not truly understand soft. In fact from a post back in 1996 I was advocating they should be thinking more like taiji soft and learning to train and use the waist, hips, and upper body separately and then as a unit in motion, instead of their versions of the Yoshinkan, and aikikai "frame stances" with their bowed back and stuck out belly's. Which, by the way- pretty much had you screwed before you even started.
Soft
You know immediately when you are pushing, yanking, and trying to enter to throw someone and they are standing there playing with you and wiggling and moving and they feel like a steel belted radial that can turn and move all around you but you can't do anything with them and end up on your fanny for trying that there is a Martial soft that goes beyond what the majority of folks conceived of as "soft."
But look, even with that there are ways to train that are not all the same, ways to carry the body, that are not all the same in a given art. Everyone talks about moving from the center and yet there they are in all their glory; single side weighted and onece you remove technique they don't really know what to do with force.
There is a study of how to change force, but that is a discussion best left till A-F-T-E-R you start learning to knit your body together. Well, okay, during as well, but only at certain points. The reason for that is trying to accomplish certain things with a normal body is waste of time. Getting someone to stop single weighting themselves or breaking when they are standing there all by themselves is one thing, getting them to do it against a single line of force, another, getting them to do it against fast changing motion that is soft itself is another level still.
Suffice to say there are ways to change incoming or pulling or turning energy -within your own body that scapulars and sacrums don't even come close to touching. Stepping into the use of spiraling energy alone is a world of work, past basic solo frame work. And it requires years of investing, not a few weekend seminars. You can try to get it from kata, or you can start to train by yourself and become something different to the majority of players out there. But you need to find someone willing to invest in you as you work, and for many -maybe being willing to give up going to X or Y seminar this year and instead focusing on the change in building a bujutsu body to fully express a Budo art.
I am actively getting teachers involved so they and their students can focus together and make the change. It seems it will be far less frustrating for both parties as "the crucible" in which to build- will be right there in their own dojo. And the testing ground -out there against Shihan-will turn into nothing more than a playground for people who are doing the work. I think of it like a grand experiment, as well as being a hell of a lot of fun.
I think everyone needs to make a committed step and stick with it. Picking up this or that "trick" or this or that "part" isn't going to accomplish anything truly meaningful. It's what everyone has been doing for years in attending so and so's seminars or having all these teachers in with different methods. For years I have looked at certain teachers who invite all manner of Budo greats in for this or that seminar to pick up this or that. It's great to be so open minded but more than a few times I have looked at those guys-a few of whom were and are friends of mine and said.
"That's great. So what happened to you?"
Cheers
Dan