It isn't the height of the fence that counts, it is the quallity of the fence that counts.
I would highly recommend going on the Lunge Line - Reinless.
At the Spanish Riding School, riders are put on the Lunge Line for a full year before they are given the reins - no wonder they have such phenominal seats and legs.
GP Level riders go on the lunge line to tweak themselves, I go on the Lunge Line to tweak myself as well - the Lunge Line is a GREAT way to repair, fix, correct, train, re-educate, educate our seats, legs, body position and re-establish the more important parts of our bodies when we ride.
Go on the Lunge Line, reinless - and start working on feeling your horse. Feel his rhythm, feel his movement. Learn to grasp a natural feel for where you are, and where your horse is.
Work on balance, work on your lower leg, work on your seat and the rest of your body - to remain with your horses center of gravity, to remain functional. I promise you, you will quickly find your seat and figure out how it is supposed to work, and your legs in accordance with your seat. You will learn to control your horses tempo and rhythm through your seat and through your legs.
Then, when you establish that - merge to Trot Poles and Cavaletti's. Remain with your horses motion, rhtyhm, movement and learn to allow your horse to move you while you remain over your hoses center of gravity.
Then, move to x rails - same thing. Learn to focus on your horse - where you are, where he is. Learn to ride his rhythm and allow his movement to move you.
When you learn to stay with your horse, when you learn to allow your horse to do his job, when you learn to stay over his center of gravity and allow him to move you - then you are ready to go back to 3'0" and bigger.
That's my suggestion. It works like a charm -and you will become one strongly established rider who will knock the socs off of other riders in the show ring.
I DO NOT want to be riding with people saying "Oh dear, she should not be jumping these jumps! Look how far back that lower leg is!" Or should I remain at the height I am at and focus on my problems there?
I wouldn't be too worried about what others think. Believe it or not - many don't know what proper equitation is because they aren't being taught properly themselves.
Uneducated are teaching the uneducated.
Again - it isn't about the height of the fence that matters, it is the quallity of the fence that does. GM Preaches this all the time and I highly agree with him.
Rememer, we are here to represent our sport to the best of our abillites. Our horses as well. We are a team, we must work together. If you are out, so is your horse - you are there to bring out the best in your horse every stride you take.
Focus on your problems.
You know you can jump, your horse clearly can jump - why not make it better. Don't work on what you can do, work on what you cannot.
It'll take time, but when you accomplish this - you will knock the socs off of other equitation riders out there.