grafting questions

is it possible to push a scion and root stock together with too much pressure and inhibit the formation of connecting tissue?

Surely a question for the master grafter - Luc.
Other than pushing SO hardthat you actually destroy tissue, I cannot imagine this to be a problem.

I don't think so Dete. As Hetty said, as long as you aren't destroying tissue, tighter is better. The scion and root stock will naturally push apart as the cambium expands so you want to hold them together tightly so that they will join.