Based on the R-1830 and R-1820, probably 1/3 of your current light weight is going to be the engine, which is a pretty high percentage of the weight to be tied up that way. By the time you've accounted for the crew and the MGs, you're probably at 1/2 the light weight (I'm not including the ammunition for them, just the MGs and their mountings themselves). I suspect it's going to be simply too small as currently listed. I mentioned the Val because it's a plane that did the same role, had an engine of about the same size, etc.
The revised warload's an improvement.