Honestly, i would try some good insoles like Superfeet or the like and replace your insoles.
I bought them for other reasons(after seeing the cheap paper shit that was in my Rulers), but they also had the added effect of raising my foot up slightly higher in the boot all but eliminating my heel lifting that would happen. The boots fit even better(they felt great without) and i couldnt get the leverage to lift my heel while on my toes edge.
'09 151 Never Summer SL-R
'10 K2 T1 DB Bots
'09 Burton Cartel Bindings