Robert Jackson wrote:
Just to add a little flair body size of the Uke or the nage?
Both matter... As a 6'3 guy there is no way I'm going to do Shihonage on some 5'0 little person.
And at the same time no 5'0 person would do Iriminage on me.
However, thats not saying the 5'0 person couldn't effectively do Sudori..
I disagree, Robert
It is more like Marc said. Size might limit the situations, where a technique should be effectively apllied and certainly dictates, how a technique must be applied to be effective. Unless there is no size at all.
As long as ukes hand can reach your head, you could do a shihonage effectively. In the case, you mentionned, it might not be the first choice in taichi-waza (both partners standing), but is still possible. Much more likely you would want to use it in hanmi handachi (nage sitting, uke standing). So some schools tell long students to go down to there knees to apply shihonage easily. That is one way, but not the only one.
For short aikidoka to apply iriminage on long partners, it is much easier. It all depends on kuzushi (breaking balance). If nage is able to get uke down, it is easy to apply the technique.
The funniest demonstration, I have seen was by Mitsugi Saotome Sensei. He took the longest and the shortest attendant of the seminar and showed, how not to apply a technique and how to change to make it work.
So my experience is, that size is not very important for effectiveness of aikido techniques, but when and how to apply the techniques effectively. And yes in each situation there is one technique, which would be the best choice. While it is too difficult to determine all parameters to find this very best technique and its application, with some experience you might find easily a set of eligible techniques. Game theory says, you should choose one of them randomly, because you would otherwise change the situation by giving uke hints about what he can expect. And usually an expected technique is less effective than an unexpected.