easy solution, cut a piece of foam (high density if pos and sticky backed) in a upside down V shape and stick it on the back of the liner just above your heal (exept cut the point of the V off so its two strips down the side of your achillies) this will nip the liner in and stop your heal lifting, im a boot fitter btw and have done this with my boots cos the liners packed out alot and cant afford custom liner, hope this helps