I can't help you with the aiki taiso. However I know about starting at the beginning. I never made it to Shodan and had to move to a city that had no aikido in my youth. Well life happens and after over thirty years walked back into a dojo. You will find you own level. Trust in your Sensei in this matter. I had some body memory but since the organization was different some of the techniques were different enough to be frustrating. I started at the very beginning. Honestly I do not bounce as well as in my youth. This is a barrier. After 2 years I am not back where I was at the age of 15 in many ways. I found that for me the best approach for me was to bring beginners mind to class every day. Some stuff will be different. This is natural. You will do fine and find your own level much like a bubble will find its own level in water. Good luck to you and happy training.