Being a strictly 7-string player with lots of BKPs I thought I'd chime in!!lol
I think you'll be ok with the RGD7320.
I have had a few plastic pickup rings that covered 7-string BKP are very tight in, so I've had to file away some of the inside edge of the plastic pickup ring for it to fit, but I think RGD7320's dont have pickup rings anyway, so I think thats irrelevant!?!
And there have been times when I've had to file away the corners of the pickup mounting ears (the part of the baseplate of the pickup that the screws go through to screw the pickup into the guitar) if the guitar has tight triangular shaped holes for them, but it looks like the RGD7320 has square holes for those so I think you'll be ok :)
If anything, its highly unlikely that a pickup wont fit at all, it might just need a bit of filing if its tight (in my experience anyway).
Hope it all works out for you - maybe we could hear from someone with an RGD to be certain.
(and I flippin love my aftermath 7's, hope you love them too)