Man, ive sent plenty of non monster (some monster) planes home packing with just the two 13mm, let alone my fantasy of 4 
The 410 handles the extra 1000lb's of rockets pretty easily without being fazed, so 2 more barbettes on the already existing mechanism might of been ok 
*sigh*
Not sure which plane you've been flying with the 4 air to air rockets on them, but the 410 is a dead dog instead of just a dog when the 4 rockets are mounted.

FWIW, I've recorded the different weights each weapon package has. For simplification purposes we'll say all of the packages include %50 fuel (40min in MA) and 4/13mm MG's:
+2/20mm: 21118 lbs (base package)
+4/20mm: 21689 lbs
+6/20mm: 22198 lbs
+2/20mm & 2/30mm: 22479 lbs
+2/20mm & 1/50mm: 22601 lbs
As you can see, having just the 50mm adds almost 1500 lbs to the plane from the base weight that is shown in the speed/climb charts. The 410 is a different bird once the weight is piled on, the same cant be said for the Mossi Mk IV and 110G-2. It seems to be that the 410 is very adversely affected by any extra weight in handling and acceleration. I've not tested the top speeds just yet, but will.