Super Nova base mount

[rusty4269]

I know this has been discussed a thousand times but I'm still unclear on the subject. If I understand right the Weaver 423m is too long but the screws are the correct length. And the 93A is the right length mount but the screws are too short. Feel free to correct that if I'm wrong. I also understand that most super novas a tapped n drilled from the factory, mine is not. So my question is, does it really matter if the mount is to long? Can I just move it forward a little and drill and tap it there? Or can I buy both mounts and mix and match parts? Or is there something I'm not seeing? Is there another base that would work better? Any info here would be appreciated.