Quick cheap and easy ideas.

won't you have to loosen up those nuts as the tree grows or it will split/break the wood? a ladder stand I hunt out of (not mine) the tree has grown around the metal bars of the stand. it is secure as hell but it sure isn't going anywhere else.

I'm sure that is the case.. That's what I figured or like you said you would end up over growing the 2x4s or splitting it.. Most likely the latter.