One thing about ours...we raised the original design by 7"...this made the headroom underneath just about perfect. The width is also just right, and provides a slight slope outward at the bottom when the canvas is installed, but the frame is a bit too wide when going thru the locks...care must be taken by having the wife stay on the opposite side of the boat to keep the rack from hitting the lock wall....larger fenders would also cure this.
I doubt that my entire rack weighs much more than a heavy duty radar arch. The tubing is 1x1 thin wall, and the arched shape gives it the strength that it needs to easily support the canvas.