“Can these be used to store a 14 foot polyethylene canoe of about 75 lbs.? Willing to use 2 sets of keeperz (4 straps) for support and to prevent warping. Has anyone stored a canoe like this? Also, can these be mounted to garage rafters to store the boat in a righted position if side storage is contra-indicated on a canoe?”
I would think that these would work fine for your canoe, based on the information that you have provided. These should work fine being mounted to garage rafters. Four straps would lessen the stress points versus using just two straps if you choose to do that, it should help to prevent warping.