The Hellboy has the compound radius - not the standard.
By the way Dingwall's compound has alway seemed excessive to me (25''/7.5'' = 3.33 so the string spacing should be over 3x wider at the bridge than at the nut, which it isn't).
I asked Sheldon about it during a live Q&A months ago where he confirmed my understanding of the concept was correct, but their stated radii also are, which seems mutually exclusive.
Does someone know what's up? It's not essential for me to understand, but I always prefer to.
The Korean factory has the capability to do compound radius FB's whereas the Chinese factory does not. So both Hellboys and Standard 5's are compound.
I've seen formulas for calculating compound radius variables. They didn't make sense to me, so I used CAD to model the arc at various points on the fretboard while keeping the path under each string perfectly straight. I attribute that to why our radius values are different than the norm.