... I like the Wag seat belt setup and it's inexpensive but it would have to be left pretty loose in order to lean forward to get to the trim and carb heat. Pretty much necessitates an inertia reel. Not that I have anything against an inertia reel necessarily except the cost and having a big reel in the baggage area....
The old methods, above, are the best.
The Wag and CC belts are a pain to put on. I wish they would switch to plug in like Scientific Pacific uses on jets