Replying to New boot binding adjustment

Looked in the stickys and searched bared but nothing specific enough, BTW I understand that this advice you give me is to be done at my own risk Blah, Blah, Blah and I have way better things to do than sue Newschoolers

i got new boots which are about 10mm longer than the set up of my bindings is it okay to just adjust them or do they need to be remounted, also should the boot be a very tight fit or able to move a tiny bit? Would i need to adjust my DIN for longer boots?