The JB weld is holding. I took by time prepping the surfaces. After letting it cure for a day I tried laying the saw on its side with the rod completely horizontal. I think that is the best test of the joint. The weight of the power head would be trying to spin the threaded rod. No problem that I could see. I'm going to let it cure some more.
The weight of the ball and steel was more than enough to balance the saw even when pushing down on it.
I think I'm going to like working on carbs at this height and angle.
I'm really happy with the way this turned out. It took a while to get the front 2 rods set to the correct height. Now that I have those locked down I can move the saw and hand tighten the back bolt to hold the saw in position. It'll hold but I use a wrench from there to make sure it's stable. 1/4 turn does it. A 2" lever welded to the rear nut would be sufficient. Otherwise I didn't have to weld anything.
The lower piece of steel keeps it stable without having to bolt it down. I pushed it to the back right corner of my bench after taking the pics. If you had more bench space you could get rid of the lower piece and bolt the lower rotor directly to the bench.
Cost was around $30 if you include some JB weld. I could save a bit by getting rid of the coupler. I'd like to mount a vice on it at some point so the coupler is nice.
Make sure to post a pic in here if any of you guys end up making one!