Before you get the 8000 pack, just make sure that it will fit under the body with the battery trays that you are using. Even the 8K pack is pretty big. What you should really do is make up some mock battery packs with cardboard and make sure that they will fit. Running 16/46 with the 8XL and the MM, the 8XL got hot. On occassion, it was too hot to touch. IIRC, 180s or so. The Feigao motors are great for the money, but they are inefficient. They are going to get hot. It just takes longer.

I mentioned the 5K packs because you said something about the maxamps packs. I run the Kokam 4800 packs and all I can say is that I get at least 15 to 20 minutes out of them (running 14/46 gearing). Since I run with nitro guys, I just change batts when they shut down to refuel and lets their engines rest. The batts are about depleted by then anyway. I've just never had the LVC cut out on me, but it wasn't far off.

I'll tell you this. 16/46 is going to be fast. Probably faster than any nitro on a track. I don't think I ever clocked my setup, but it was fast enough for the track. At 14/46, it is competitive with the nitros which is fine for me.

If you are going to be running a 4S setup, you might want to consider getting some really good batteries at some point. Don't get me wrong, I'm a big fan of maxamps products as far as bang for the buck goes; but I have gotten even my 8Ah packs pretty close to their temp limits. Since I've gone to the Kokams for my 4S configurations, I haven't had to worry about the batteries over heating. The flightpower packs are really nice and will dump current on demand without breaking a sweat.

I know that cost is a concern, but you really do get what you pay for when it comes to lipo packs. One of the reasons that I went with 5S was so that I could have a lower current draw system and be able to run less expensive packs. I'm running a cheapo truerc 5S 8Ah pack on the 8XL with a Compro controller and the battery doesn't even get warm.

As far as I'm concerned, I think that you should go with the 8Ah pack, if you have the room. If you don't, then look at the 5Ah packs. What ever you do, you have to run some sort of heatsink on the motor and a fan on the esc.