Since, like now, I was nowhere near having a proper bed constructed, I built this test bed for the golfball mortar out of whatever wood scraps I had at the time:
To get the bigger tube to sit properly in the bed, first I had to open up the notches. 1/8" farther back and 1/8" deeper to accommodate the larger diameter trunnion (1.250" vs. 1.125").
Then bevel the inside edges for the butt to clear, and finally shave off the wedge to get the correct 45° elevation. Overbuilt in the beginning so opening it up wasn't a problem.
I will have to plug and redrill the holes for the trunnion strap screws, since they had to be moved farther out to clear.
I used #12 stainless screws in the straps. I wasn't sure what to expect, so I wanted to make damn sure that even if this thing flipped, it would stay bolted in.
Not a problem, it handled the golfballs well. But with the poolballs it might buck a little harder.
The oak bed will be bigger, and a lot heavier.