How to get better position/eq over fences?

I have decent eq on the flat but over fences its a 50 50 shot. My horse has trouble juding distances but it doesn't give me and excuse to have a bad position. My trainer and I are working on it but I only have a lesson once a week. I seem to stand up in my stirrups when I jump yet if I shorten them, they seem to short and feels uncomfortable since I am used to riding in semi long stirrups. Is there ways that I could improve my eq over fences during the rest of the week so I'm prepared for my lessons?