I don't know what the problem is? Many years ago George Campbell use to instruct at Mudgee. He was 150kgs and only 5ft 6. When he got in the C150 it was a sight to see.
Notwithstanding George was a sought after Instructor as he had the knack to making a pupil feel at home.
You may have to learn on a C172 as it will be easier to get into rather than the Warrior types. It also has a better seat adjustment, especially later series ones.
Just remember you are a client who is spending money. Don't talk to the young instructors, go and speak directly with the flight school owner, after all he has a vested interest.
For what it's worth go and have a talk to Guy Pearson at Essendon. not cheap but good value and has C172s on line.