To make the topping lift adjustable, I have it (1/8” dyneema) spliced around the backstay pin at the top of the mast with a tiny micro block (Harken #404) on the other end about 1’ above the boom when it’s at a right angle to the mast. Then run a second line (5/32” Dinghy Pro) from the end of the boom, through the micro block, back to the end of the boom, and forwards to the mast. That gives you a purchase and having it at the mast means I have my reef line, lazy jacks, and topping lift all in one spot.
This may be easier on the Z Spar boom because everything is internal and the boom had 2 built in sheaves on the outboard end.
Purple is the outhaul, orange is the reef, and red is the topping lift. Reef and outhaul are cleated by the mast.