I tried what the two above said, and it would not work for me. The hole say I was using kept grabbing the tubing and twisting/flinging it. I cut my trees on a miter saw and used a belt sander to cut the cove. The top one is at 50 deg. ,and the lower one is at 45 deg. The top holder is offset forward of the lower one also.
I also made a launcher that slips into the trees.