What do you mean by too long? Do they draw past the rest and fall out, or do they just not stick out past the riser? A proper length arrow for a modern compound is not supposed to stick out past the riser. The tip should be over the shelf towards the front edge of the bow.

If you can draw your bow back and the arrow comes back so far it fall out of the rest something is wrong. With a 29 inch draw length and 29 inch arrows your arrows should actually be a tad long, not short. If your set up is what you say it is the end of your arrow should line up with the front edge of the riser or extend past it. NOT come back far enough to fall out of the rest, any rest unless it is set up wrong.

I would suggest verifying the actual arrow length and your actual draw length. I think one might be off.

With a properly set up prong rest your arrow would have to be near 2 inches shorter than your draw length, and with some of the newer type drop away rests and the WB rests it could actually be shorter because they mount behind the shelf, not over it.

Paul