I don't think, that Conshox is supposed to float that much as you imagine, as it would leave rear binding open and moving/rotating and it would be Bad Thing . This pinching shouldn't be problem, I'm sure, that F2 engineers have figured it out, after all snowboarding ain't rocket science :D So you should not bottom screws to inserts, instead there should be some space left (at least one thread, as with usual mounting).
I use currently F2 Intec Titanium bindings, previously I used F2 Intec Titanflex (for which I bought separate screws, as thanks to higher binding plate original screws, provided with Conshox, were too short). And I mounted them as usually, tightening screws as much as possible (without overdoing it) and checking them from time to time. My board is Silberpfeil, which is Conshox 'compatible'.