heyo. i agree with mr freeman.
teachers are there to advise on standard and tested methods.
however, everyone is built differently. for example i have to adapt my forms slightly from the standard version because im short and light compared to most of the blokes in the dojo. however, i only do this when he advises me on whats best after seeing that the original way doesnt work (im not confident at always finding my own way yet as im just a novice)
martial arts are a sbjective thing that still try to find a standard way so as to keep order and not loose teachings of their founders.
theres a guy in iai who has balance problems and has to adapt his waza quite dramatically in order to make them work for him and so as to not fall over.
i would try moving on the balls of the feet a bit longer until you get used to the mechanics of aiki. it could be that your body is just not used to moving in such a manner. however, if it causes pain, complete lack of balance or risk of injury, stop and ask your teacher te best way.
i have a question to add to this thread myself if thats ok.
doing irimi tenkan etc, i keep getting told off for pointing my toes in whilst doing the step forward. i can see the logic in that if done quickly one can risk going over on the ankle. however, it hurts and i find it harder doing it with the foot straight. its the wrong kind of 'hurt' and 'harder', as my foot naturally moves toes in when i step forward due to a knee injury in the past. it put pressure on the knee if i try to step with the foot straight, then i cant tenkan smoothly.
forgive me if i have answered my own question already. but any advice would be greatly appreciated. ive tried explaining it to my teacher and my problem with tight muscles but he doesnt seem to want to listen.