I strongly recommend against shortening the chamber. Towards the end of a pressing, the plunger is pushing air through the grounds and extracting flavorful brew. If you shorten the chamber, there will be less air pushed through the grounds and they will be soggy, leaving a lot of tasty brew in the soggy grounds. Incidentally, the amount of brew left is the AeroPress "puck" is about equal to the weight of the dry grounds. The amount of brew left in used pour-over grounds is about twice the weight of the dry grounds. So the AeroPress delivers more good brew to the cup.