Hey Barry, I have a single bolt adapter (SBA) for my RCGF 32 and I like it fine. I bought one for the DLE 30 and it sheared the bolts and threw the prop during its maiden flight.
VVRC very kindly sent me a replacement, but when I put it on it showed excessive runout.
DLE 30 - Single bolt prop adapter - face runout
DLE 30 - Single bolt prop adapter - shaft runout
I let them know; after a reply email I checked the fit and found the cause.
As you may remember, to attach the SBA you have to make a nut out of the crankshaft extension by cutting off most of the shaft.
I discovered last night that the nut is too long, interfering with a flange on the back of the SBA and preventing the rear of surface from mating flush with the face of the prop hub.
I was able to shorten the nut by removing a portion of the flange at the bottom.
Now the SBA fits properly - the flange fits in the bore of the prop hub with no wiggle room that I can see.