Not helpful at all, but when i was 6ish my riding instruct wrote a million pound cheque(ovb not a real one) and put in on the saddleseat, we had to stick our bums down to stop it from flying away. Lol
Pilates is great if you find the right teacher. Try and focus on the quality of the movements, not the speed and reps. It helped me strenghten my core which in turn improved my riding no end.