So, I let the JB weld dry for 24 hours. Actually, a little closer to 29 hours or so
Carefully peeled the masking back, and sanded both sides flat.
Took a .156 header, and removed 2 pins. Carefully enlarged each hole in the header housing to fit a small drill bit to put a pilot hole in
Enlarged the pilot holes to the correct diameter for the eyelet, and inserted 1 eyelet
And, the JB weld cracked after a few taps with the tack hammer to set the eyelet.
Looking at the situation, I wondered if maybe the JB weld is too brittle for this. But, looking at it a little closer, I don't think that's the problem. The JB weld is strong enough. The problem is, I believe I need some support around the eyelet as I set it, so the board isn't flexing while I hammer on it.
So, I'm going to mask it off again, load it up with filler again, and let it dry for another 24 hours. Thinking perhaps I need to put a piece of hardwood under the board when I set the eyelet. Perhaps take a piece of hardwood, bore a hole big enough for the eyelet setter to slide through it, and then rest the board on it to provide support outside the actual eyelet area. Hard to describe...
I think also, I need to sand the JB weld a bit more, and get the top and bottom of the PCB perfectly flat. The eyelets are sized to the thickness of the PCB. If the board were thinner, it wouldn't be as big an issue - but if the board is thicker, there's not enough eyelet material to create the top 'flange' when you set it.