I got to use System 3’s Silverthane polyurethane sealant this weekend, in place of 5200. http://www.systemthree.com/store/pc/SilverThane-SA-2100-c58.htm
It is a 2 part product so that seems to solve my two main complaints about 5200; that my $17 tube hardened in just a few weeks, and after seems like days, the part I sealed was still wet.
I lose 5200 tubes after they opened even though I try to seal them up.
The two part poly self-mixes in a special nozzle. I’m guessing each use ruins the nozzle, so get several if you work like I do, with several small jobs. And my job was functionally cured the next morning, which was the soonest I tried it.
Only comes in white at this time. So I still have to bear with 5200 for black jobs.