If you leave holes open up front, just open a few in the very back of the plane to allow the air to flow thru the entire fuse. I have some holes on the bottom right in front of the tailwheel bracket. While I have not heard of the air pressure blowing off canopies or hatches, I have heard of it blowing of pieces of covering.

Another reason a lot of guys leave holes in the front and the rear is to help discipate heat. Kind of like a flow-thru cooling effect. I do this to help keep the radio gear cooler since the radio floor is also the ceiling for my cansiter tunnel.

............Mark