Hey Ryan, long time no see..
I do agree that the Traxxas board isn't that much help.
I think if you want more power without more cells, maybe the thing to do is to go for a different power supply in which would be Li-Poly cells. Now from that point you will probably lose a bit of weight and gain a bit more power because you could probably get more voltage.
Now that being said a li-poly cell is about 3.7 volts but at full charge they are about 4.2 volts so say you use a 5s pack which would at full charge give you near 21 which would be much more than what you feed it with 16 cells. So it would be like almost running it with 18 cells Sub C NiMH.
Well from that point, if you want more power is to upgrade to a bigger badder motor.
The 7XL might be a bit more powerful motor on paper, but also on paper it would be more powerful by like say 200 Watts. Tho the BigMaxximum I believe has more torque due to the 4 pole design. Now the question is whats more efficient at its voltage ranges. Anyhow my point is the 7XL might be more powerful on paper but if it is, it isn't by much, personally I like the BigMaxximum better but thats me. I do have a 7XL and I plan on running it a bit more than the small testings I have done but with a 9918 controller in the future.
Actually now that I think about it maybe you should try the 7XL motor because its a great price, just to test it out and see how you like it against the BigMaxximum, maybe you might like it better.
The clear upgrade in my opinion from the BigMaxximum I can think of is a 22 series motor from Lehner. Now the 2230 series are the lightest of the 22 series so I would start there but I have no clue on the turns unless you know what is a good kv rating for the motor you want then you can start from there on picking your turns on the motor. If the 2230s don't satisfy maybe go for either a 2240 or a 2250.
Anyhow these will have a higher output than a BigMaxximum or a 7XL, probably a much bigger motor as well.
By the way I would try 18 cells first. I don't think adding 2 cells on to that Maxx Bling will hurt it much.. hehe.. look at mine, it fits well with 18 cells.
Your truck has gotten much lighter since its inception hehe..
Mine at this moment weighs with everything on it on 18 cells
12 lbs 14 ozs which is in grams about 5840g.