I'm not sure about seat belt decals, since I'm sure it must have doubled back on itself quite a few times, but I've used Microsol and even Solvaset on Tamiya decals and the key is to be patient - put the stuff on, try not to look at the decal shrivelling up, for darn sure don't touch it, and leave the room to watch TV!!!
I was building a F4D skyray that had a decal to cover each side of the tail. Not surprisingly, such a large decal had a hard time settling down over details and into recesses, especially around the rudder. I used Microsol, it shriveled just a bit and I gasped. Knowing anything I would do at that point would make things worse, I left the room. Came back much later to find the shrivelling gone but the decal still hadn't settled down very well. So I tried solvaset - this time it REALLY shrivelled. Convinced that "now I had REALLY done it," I called it a night. Next day, the deacal was laying down flat as if the design had been painted on.
Anyway, that's my experience with Tamiya decals and strong solutions.
Cheers!