First ask somone who does trials if you have the right tecnique. Then, I know you're probably sick hearing this but practice, practice, practice and you will get higher.
I was looking on tarty for a new freewheel and in additional information it said for all them "may not fit bashring setup" but my bashring also acts as a spacer so im stuck really. Does anybody know a freewheel that's durable, long lasting and allows a bashring setup