Thanks a lot for the bolt size and the hole spacing, Jeff.
I think I'll go with the TS Optics clamp as that one has a pair of smaller thumbscrews, so they should clear the DEC motor housing without the need of a coupling nut.
Scopes: APM-LZOS 115/805, Skywatcher 200P Dob & APM 107/700 (grab'n'go)
Mount: Skywatcher HEQ5 Pro w/ Rowan belt mod + ADM saddle & ES iEXOS-100 PMC8 w/ Fine AZ adjuster + ST2 tripod
Eyepieces: ES68 34mm, 24mm; Pentax XW 14mm; ES82 14mm, 8.8mm; Baader Morpheus 6.5mm, 2.25x Q-Barlow; TV Delos 4.5mm, 2.5x Powermate
Imaging: Canon EOS 600Da, Canon 135mm f/2L + 1.4x extender, TS 2" 0.79x FR/FF, IDAS NB1 triband filter, Altair Starwave 50mm + ZWO ASI120MM Mini (guiding)
Software: BYE, PHD2, ASTAP, Cartes du Ciel, DSS, PIPP, AutoStakkert2, PS CC
Binoculars: Vixen Ascot ZR 8x42WP