So part of your question is do you like them, do you use them. I dont, I have fixed diamonds that I rarely touch.

If I was going to do it, I would make each side adjust independantly, give you more flexibility in the adjustment.

I dont think you need to overly reinforce the mast, the point that the lever arm goes into the mast might need some reinforcement, but I'm not sure. The blocks need to be wire line blocks, not regular exit blocks.

All the attached pictures obviously have internal downhaul and diamond tension setups, not sure the purchase or how you fit all those blocks in the mast.

Bill