Somewhere your weight numbers are off. I tried to copy this in MML and it comes up as way way overweight. Base version should only be able to carry 6 (1x4 & 1x2 stacks) and have 10kg leftover at 6 armor. The LMG version is over weight by 30kg. Variant three is actually illegal (or at least, in MML 0.49.2 which is what I use) as you can't fit 7 points of armor on a Light BA, it maxes at 6. If you drop it to 6 points though w/ Standard Stealth, then its exactly 750kg.
Its probably that glitch that MML has where if you swap between VTOL and Jump it occasionally gives you VTOL move, but using the mass for max jump only. Dunno how you got the 7 points of armor though.
Alternatively, if you make it a mixed tech design with an IS base/frame, then you've got more than enough mass freed up to do exactly what you planned.