I didn't talk with him about this yet. I just think that even if he would sincerely offer me a maximum X, an hard pressed negotiation would still give me 1.05X (annually it's not a small amount of money...).

EDIT: as you say "with that kind of mindset you will either press too hard and lose him (and potentially the offer too) or you'll end up feeling resentful at being "underpaid"."

What other mindset would you suggest?