I have good luck with using a squat bar with mamas with epidurals. We set up the squat bar, then put the foot of the bed down and the head all the way up in a chair like position. The mama then needs to sit right at the edge of the upper part of the bed with her feet resting comfortably on the lowered foot of the bed. During a contraction, we help the mama come forward, holding the squat bar, and help her sink down into a true squat. In between contractions she can boost back up a bit onto the edge of the upper part of the bed again.
Also, I find a lot of mamas are able to do hands and knees if they aren't completely numb. We raise the head of the bed again so she can rest her arms over the back.
If a woman is very numb and can't sustain any position using her legs, you can still put the bed into a chair position to allow the baby to labor down until she feels an urge to push. (High Fowler's position they call it around here.) Even very numb women can use side lying, and this at least gets the sacrum out of the way.
Standing or squatting more freestyle are often difficult unless the epidural is turned off - although you have to take it on a case by case basis because sometimes as the baby descends women seem to regain a fair amount of leg mobility, and some women aren't very numb to start with.
I don't have any where near the 97% epidural rate, but I try to use upright positioning as much as possible to help counteract the tendency of the epidural to slow descent. I'd say the biggest challenge is not how much the woman is able to move but how willing the staff is to move all the stuff - epidural catheter, IV tubing, bladder catheter, monitor cables - and then move it again as the mama freely chooses a position. I'm fortunate to have really good nurses where I work who think nothing of helping someone all bound up by tubes move every other contraction if needed!