Quoting Josh Guilbert
90mm gun? 90mm is WAY to large for a plane of this size to carry.You couldnt hold a good number of round's to.And in WW2 the US captured an ME-262 with a 50mm cannon in the nose capable of downing a B-17 in one well placed shot
Why not? Like you said "a 50mm cannon in the nose capable of downing a B-17 in one well placed shot", so a 90mm anywhere was a sure hit. And 5 rounds was enough to shoot down five bombers. Even if it“s to large for a plane of this size, it“s not a problem. 4 30mm guns make more recoil for 4 seconds firing than a single 90mm gun firing one round.