Re: High Ukemi Help?
I have seen this kind of exercise at some dojos and never understood its practical application. Even on big koshinages, uke's role is not to launch himself over nage but to attack with energy and take the throw as nage does the throw.
I know that isn't what you are asking - I guess I'm trying to provide reassurance that difficulty with launching high in the air should not impair development in aikido.
But if this is an ability highly valued by your instructor, my suggestion is to either keep working on developing the skill or get help to figure out if there is something inherent in your body that makes you not very well suited to this particular exercise and politely bow out during it.