What do you want to carry?
I carry full size canoes and have done for 5 years now and wouldn't consider an inflatable rack or similar device under any circumstances for this task.
Why?
Well,from what I've seen of them in action: first off, you do indeed get "nodding" even when you cam strap front and rear.
Then you cant wrap your main straps around the bars, so you're relying entirely on the integrity of the stitching and materials the inflatable thing is made from, to keep your load in place. I'm sure they're rated to suit the job but you cant always see dodgey stitching as easily as stripped screws, wear marks or cracks, like you might with a metal rack.
A third issue, at least with boats, is that you almost always pick up sand and bits of stones or gravel etc which, no matter how you try to clean the boat out before car topping it, always seem to appear in the streams of water that flood out from gunwhales etc everytime you brake, pull away or turn within the first couple of miles of setting off home. This sand and gravel either washes off or drys and blows away if you have a proper rack fitted. With an inflatable set up, some of that sand tends to end up between it and your roof, creating interesting wear marks and scratches. I've seen the scars to prove this, not an issue for some folk but no good if you need to look at re-sale/trade in value of your car later on.
And the real "pita" is that no matter what you do, if it rains, the inflatable rack securing straps act exactly like wicks! leading, if not actually drawing, water straight through the door weather seals and all over you, your passengers, the carpets and upholstery.
I'd have a good think about it if you want to transport full size canoes in particular or anything actually, if only because of the water ingress issues.
good luck regardless
all the best
Steve
