With those materials,good glue lines,and a good tiller I'm sure it'll go to 28" no prob....BUT WHY...it'll just be an overstressed stacking pos bow IMHO. Why not tiller it out for a kids bow and give it to some needy lil soul,or someone with a 24" draw,or 26" max draw etc etc...
If ya do wanna take it that far you'll need to get lots of bend going right thru the handle and fades...but not too much of course.