They're going flat after bending, which gives some weight to the stretching theory.. but these have been on for about a week now, and while I'm used to nylon strings taking that long to settle down, my memory of playing electric is that they were usually sorted in a day or so. I pull them away from the pickups to stretch them, but maybe they could do with a bit more.
I always just blocked up the trem cavity in strats but haven't done it yet with this one. Is it better just to chuck a couple of extra springs on so it won't move?