[frizzen]

Good call on the hs-645 being easy to mod to contious rotation. I had all 4 servos swapped pretty quick.
Verify it works, open up, unscrew pot retainer screw inside, remove the output gear, support the gear on a v-block or pair of pliers and bump pin out. Reassemble, lube gears, verify ops and center pot. I may swap the pots out later for matched set gold band resistors if i'm in there sometime later...

Have they been looked into enough to see if there's a way to open up the deadband a bit wider?

Were the shafts you used made from piano wire, or from a certain donor?