I believe you will find aluminums difficult to tune with points that heavy, regardless of the spine you choose. In my experience, once you do achieve a tune they won't be very forgiving, for example a poor release will really show up in arrow flight.
I like aluminum arrows, they have a lot of advantages, but if you really want to shoot 250 grain points I'd suggest you consider carbon. At least you have some 2020's to play with to see if they're going to be a viable option, I would think the 2020, 2117, 2216 range would be your best shot in an aluminum shaft.