I have a hard tail Giant XTC1 2010 medium, being 5 11" and 80Kgs I am at its hight max

I'm more than comfortable on the bike but ride with the seat adjusted as far back on the original post as it will go. often if i come down hard on the seat it will tilt back, which is not helpfull .

Question would a new seat post like a layback seat post help ? I.E Thomson Elite 16mm set back or simmilar.
Yes i could go a slightly larger frame however i'd like to give this bike another year yet befor upgrading

[Mod. moved to MTB gear]