What RR has said is correct, I have two MM with a HD and the volume difference is quite big, however you already have a Crawler, a strong pickup itself, so this may not concern you! the HD in single coil mode does work very well with the MM, I only have my HD as a humbucker when it is used by itself, RRs use of the VHII would work well with the MMs, however not as tight as your Crawler,