Rolled with 3M "Super Weatherstrip Adhesive" #08008. Comes in a 5oz tube, black goop, pretty watery. Closer to water than RTV. But after a few seconds of air exposure it gets pretty sticky, then in a minute REALLY sticky.
I applied a small amount to the long trim piece that goes along the upper part of the window frame to get it back into position, then a thin bead to the piece that was being replaced. Instructions say to apply it to both surfaces, but that really wasn't an option here. I did let it set for a minute and get REALLY sticky before putting things into place.
It's been 24 hours now, and I gotta say I don't think those parts are going anywhere ever again. ;ol;
Thanks for the recommendation Jim - #08008 seems like a great thing to have in the toolbox. Now I can glue all sorts of stuff together!