I put a Vudu 5-25x on mine specifically for running a pvs30. The rail clamp on the 30 will hang off the front of the handguard about 1/2” or so but it works fine. It still holds fine if I move it forward another 3/4” or so. That puts the rear recoil lug of the 30 in the forwardmost pic rail slot, so only a little less than half the mount is actually on the rail. But it seems to be secure. So stick to scopes that are really close to 12” or shorter and it should work. Also consider I’m using one length of pull spacer so I can move the optic rearward that 1/2”. Assuming comparable eye relief, you could add scope length and use spacers to get the scope mounted further rearward and therefore get more space in front of the scope to mount the 30.
Bottom line I guess is you could PROBABLY get away with a 12.5” scope if you used 2 length of pull spacers and mounted the 30 as far forward as possible, but eye relied of the particular scope would be the determining factor.
You could also use a “gooseneck” type rail riser to extend the pic rail forward, but that’s gonna make the 30 sit 1/2” higher.
