5 cell + mamba 25 in a tenth scale for racing?

I have been racing a mamba max 5700 on 6 cell nimh, first in off road stadium truck, and now on carpet in a touring car for the winter. I have never come close to needing the full potential of this system for racing on our slippery dirt track or tight carpet track; 10 cells geared up in a parking lot is fun, but not practicle for racing.
My local track is now allowing lipo in mod class, and no weight restrictions, so I was trying trying to size a motor and battery as light as possible when I found a great planes ammo motor gpmg5195 28x35 mm 2700kv 3.3 oz
11.1-18.5 volt 15amp 277 watt continuos, 30 amp 550 watt burst. @ 18 volt = 48600 so gearing is not a probleme, efficiency should be wonderfull, and the power numbers look way better than the hot 19-turns that do well on these tracks. I normally pull between 2200 and 2800 mah out of my packs in 5 minutes with the 5700. 60min./5min. =12c x 2.8amps(2800mah)=33.6 amps x 7.2 = 242 watts. Plus the 50 oz car would be roughly 10 oz. lighter with new setup. I know some on this forum are scared of five cells on even a mamba max, but the caps are rated at 25 volts on both the mamba 25 and the mamba max. On another forum I read a castle thread supported by castle employees where they very politicaly correct said, the controller is recomended for three cells, but the cap was a good indicator of what the rest of the components are rated for, I think they also said leaving a 20% safety margin would be relatively safe, just no warranty. I am posting this all as a ??? I know the people on this forum have alot of expeirence, but cant find on any forum where this has been tried. My other reason for wanting this is I have a little used mamba 25 (18t racing faded out) and would like to free up my mamba max for a truggy eventualy. Also 5 cell sounds nice in m/t would rather test on little mamba$$ and if all goes well it would be nice to have all my packs universal (small 5s 10th scale; 5s2p in monster)