OK, so I just called 3M's Marine line
(didn't know they had one) for technical support and asked them. They said the 3M 101 needs to be above 40 degrees when you're applying it, and ideally during the first 5 hours or so, for it to set properly. After that, if the temperature drops below 40 it's OK while it's curing. It will just slow down the cure time.
So the point is that I can apply it. We might STILL want to consider a heat source to warm it up and get it to cure faster. But according to 3M, the cold temperatures won't harm the bond, just the time to full cure.
So, with that being said, would you rebed your chainplates now, knowing that they had to be ready for use in a month, in New England? Highs are only around 50 up there now and probably won't be breaking 60 degrees before in a month. But if I wait to do this when it's warmer, the mast will be stepped, and that sounds like a huge PITA to me.
Certainly open to suggestions...