I'd suggest less hip turning and more turning from the waist with the feet remaining stable. Power will then transfer in a different path. Rotating on the heels is not something I would ever be doing in any type of training- for any reason.
Since long weapons were brought up, it might be worth mentioning that turning from the waist and drawing "through" the hips (with hips more or less remaining with a forward orientation and mobility is a necessity in Japanese long weapons.
The large hip turning you are doing in your Shintai jiku is also seen in various Iai, Aikido and other modern derivations of body arts. Hip turning and locking the knees to the movement of the hips (and for many the shoulders with the hips as well) has become part and parcel of many arts as they get more and more Kendo-ized, judo- ized and Iai influenced over the years. It just won't cut it with long weapons.
more waist and less hips for long weapons? don't have much experience with long japanese weapon other than the bo. for some reason the longer the weapon, the more hips i used. i would consider the chinese kwan dao a bloody long and heavy weapon, for example, this dude here http://www.youtube.com/watch?v=3t2DahSZyVg
but then again, the kwan dao, i believed, was meant for heavy cavalry troop. i don't ride horse, so do folks use more hips or less hips on horse back? if you only use your waist alone, how do you bring the power of your legs to your arms? i guess i am a bit confused on the power source for the long weapon. i guess i have to run to home depot and get meself a long heavy water pipe to test out the approaches. or could it be i misunderstood your description? very likely as well since i am not experienced in these matters.