I use fine brass wire glued to the block. Then I use a small pin vise to drill a little hole in the mast and insert the wire into the hole and glue. It gives some spacing between the mast and block. I gave up on that idea of putting a disc between the block halves also. I just folded the halves together and glued them.
Different ship but I used the Liberty PE blocks:
On the Liberty, as on this one, there is no block on the boom end, it's just a single wire attached to the ring on the boom. I didn't rig the wires through the blocks, it goes around the outside ( two step glue process) but the difference is not noticeable after the block is painted. If your booms are lifted, as when working cargo, you'll have the blocks for the running wires, at the head and heel of the booms. That was more complication than I wanted to deal with!