Oh, the above was the A-5, here's the numbers for the A-8.
190A-8 2 guns 100% (169gal): 9360 lbs
190A-8 4 guns 100% (169gal): 9682 lbs
190A-8 30mm guns 100% (169gal): 9891 lbs
169 gal = 1,014 lbs
1 gal = 6 lbs
30 gal aux tank = 180 lbs
79 gal DT = 474 lbs
950 13mm rounds = 171 lbs
500 20mm rounds = 242 lbs
280 20mm rounds = 136 lbs
110 30mm rounds = 143 lbs
1x 13mm round = 0.18 lbs
1x 20mm round = .485/.486 lbs (in/out)
1x 30mm round = 1.3 lbs
2x MG151/20 plus 280 rounds = 322 lbs
each MG151/20 outboard = 93 lbs
2x 30mm plus 110 rounds = 531 lbs
each 30mm = 194 lbs
More weight than A-5 (not counting aux)= 596 lbs
Total DT weight = 540 lbs
Empty DT weight = 66 lbs
Even without the outboard guns the A-8 is 600lbs heavier than the A-5. It's easily worth the weight for the outboard MG/FF, but as you can see the 30mms are very heavy. I wouldn't take the 30mms if you plan on turning at all. Use them for bombers, for BNZ, for HOing, or for ground strafing. Otherwise leave 'em off!
EDIT: bolded the outboard guns weapons package total weight