Get the regular - it'll set up fast enough with the temp and humidity you've got. Cure times on that stuff are slow to begin with. Bear in mind that the white 5200 is famous for yellowing in the sun. Most boatbuilders don't use it above the waterline. The Sikaflex LOT291 doesn't yellow nearly as noticeably, but 5200 takes paint better (still not really 'paintable', but better).
I don't know if you've played with it before, but it will get everywhere. I mask everything really well because it's a whole lot easier than trying to clean it up. Shape the bead, pull the tape, perfect every time. I know with a lot of painters, masking is a sign of weakness, but the only solvents that will clean up 5200 and Sika (acetone, xylene, etc) will also eat the foam....not sure how they'll get along the Gripper.
That drip cap looks great.
