Yep, thats what I'm talking about. Also I'm thinking about putting 5 turrets consisting of nothing but .50 cals, and a Tail Turret consisting of a 20mm and 2 .50 Cals, also I'm putting on a couple of AIM-9 (Early) Sidewinders for long range protection.
Of course, it is your plane, your work, but let me share some thoughts. Battle experience in Korea shows that jet fighters like Mig-15 had a little problem to shoot down a bomber (B-29) with similar gun's protection (at least if the bombers are with no or little fighter's air-protection). Soviet copy of B-29: Tu-4 moved to 20 mm and then even to 23mm cannons (it reality their effectiveness was problematic as 23mm cannons caused strong vibrations in 12.7mm turrets and after test firing/shooting the turrets had to be repaired often ). B-36 already had 20mm cannons.
Regarding missiles: early Sidewiders can be fired into jets only from the tail-direction (i.e. from behind a jet-fighter), so I am afraid that they could be of little usage.
But again: it is your idea, your work, and it would be nice to have any version of your XB-75.