How about posting a few pictures?
If the turret has 5 l/p ports chances are you have the heavy yoke. The heavy yoke screw is 9/16" as opposed to the earlier 3/8" and 7/16" screw. I've used a thinner yoke on 3000psi + tanks with no problems. Even if the yoke has a problem, it will not shear and become a skull piercing missile. It would simply stretch a bit and cause a leak at the tank valve o-ring to regulator interface. If you are still concerned about it, I believe pretty much any SP yoke will fit the MK V.
BTW Bryan has the MK 5 and 109 schematics loaded in the "manuals" section. The Usual Suspects have annotated the diagrams with the o-ring sizes.
A sincere THANK YOU to all at VDH who make this wonderful resource available and to all the thoughtful contributors.