I have had GrandPrix now for two season, very happy with them. They are high enough, and keep heel down.
I see only two things which could be better, bigger one is that top blue strap, when tightening it, that black metal piece goes sideways, it should be more tight fit to strap. Can send photo if not clear On UPZ boot that top strap could be slightly higher so it would be easier to tighten.
I know that some people, mainly Eurocarvers, prefer liner not making boot so stiff, but for me it is not issue.
For me these are perfect liners, love them.