I used the off-cut from the headstock angle for a caul. Part of the reason the original glue up slipped is I checked and found that I did not cut as much angle as I thought. I thought I had 15 degrees and it was about 11. So I re-cut the angle and trued it up but that left the off-cut at a slightly different angle which made the whole thing want to slide....and shear the toothpicks. the brads fixed that.
Edit: I have since learned that using the offcut on the bottom will give parallel faces for the clamps to push against, which is a much better method of clamping.-SR
I picked up some clamps with a Y-foot which I think I like.
I moved on to slot my fretboard while the HS cap glue up was curing. I glued it up at noon and was hoping I could take it out of the clamps and glue up the fretboard tonight. Two things worked against that. By 6:00 the T-88 was stiff but still a little tacky to the touch. It may have been fine to unclamp, but during the slotting of the fretboard, the ebony cupped too, just the like the HS cap did. I could go back to the sanding surface and re-flatten it....and may still, but first I'm having a go at un-cupping it. I soaked it in hot water and then clamped it between two 1" thick pieces of acrylic. You can see the curve here before adding pressure.
SR