I've got the clamp on racks (rhino brand I think) and have worn the paint off in parts. No dents like 26, but I think its only a matter of time. Another thing I dont like about them is they seem to work their way loose. Had two kayaks on the roof on the way home from a holiday. Had the heavy one on the roof of the cab (50kg) and the light one on the roof of the canopy (25kg) and the heavy one ended up moving the rear rack causing damage to the yak and more paint off the cabin
If I could weld, I'd love something like kwyjibo. That looks great!
Id build it in 2 pieces, one on the cabin and one on the canopy. It's a great low profile - would mean I could put the 2 inch lift on the car and still fit under our (ridiculously) low carport!
If I had to make the decision between clamp and track now, knowing what I know, I would opt for the track.