Gardens' original mainsheet fiddle-block wasn't fitted with a cam cleat, which meant I had to hold the mainsheet (which meant my hands would cramp up while sailing), but was fitted with a stand-up spring to keep the block from flopping around:
The replacement fiddle-block with cam cleat seamed to be the solution:
But... I couldn't get the fiddle-block installed with the stand-up spring: The spring was too stiff, the space was too tight, the shackle was too small, the swivel post was even smaller, and the threaded shackle pin was smaller still - it all worked against my fat fingers... My solution was a short section of pool noodle foam wrapped around the block and base:
That worked but not as well as a stand-up spring. Someone saw a photo of that "stand-up-foam-base" in a post on John Welsford's Small Craft Design Face Book page and suggested/recommended using a stand-up spring. I decided to see if I could find a "right-size" spring... The local hardware store - to my surprise - carries a fairly wide variety of small springs. But they didn't have one that would work. An Amazon search turned up a smaller (shorter, slightly smaller diameter) Harken stand-up spring but when it arrived, it didn't fit over the pad eye in the base. I decided to try the original spring again.
After several failed attempts I figured out that if I completely disassembled the base, started with the block upside down, and worked from the "inside out," I could (possibly) get the block, spring, and base connected and put back together. I only needed two more hands... My wife came to the rescue and together we got the whole thing re-assembled!
The path to this improvement to handling the mainsheet took me full circle back to the parts I had on hand when the fiddle-block w/cam cleat arrived. Buying the new fiddle-block with a cam cleat was part of the solution I was seeking. But finding a solution doesn't always mean buying a solution - I had that stand-up spring all along.
The mizzen mast project is on hold: Winter is settling in here in central Michigan: high temperatures in the mid-30s; lows in the 20s; and warmer temperatures are not in the forecast. It will be spring before I'll get back to work on the mast.