looked at mm says it 's not for 10th scale monster trucks

Well the 9920 can take more cells if you choose. It can handle 6s and 20 cells.
The mm is better in others for it has better programming and runs more than a 2 pole motor. 8xl you can start at stock gearing and go up from there.

check the rc calculator of BrianG.

with the runtimes you want to achieve, you need 8000mAh like glass suggested.

where do i find the calculater

In Brians signature.

With the 8K packs that may be possible. One of these days I'll borrow MetalMan's GPS and get a speed on my G2R.

However, I've gotten about an hour bashing on my HV4.5 with my 8000mah Lipo's. I was actually out bashing with MetalMan and he ran his BL Revo, switched to his MT2 18SS, and my 8K's still weren't near dumping.

At the track, I've gotten at least 40 minutes on my HV6.5 at race pace - so you should be able to do 30 minutes on the 4.5 no matter how you drive.

My 4.5 was running at about 95*F (101* Max) all recorded with my Telemetry. My speeds were close to that of MetalMan's BL Revo (I think he's got a 7XL and is running 5S A123 Li-Ion). It was hard to tell - we were only at speed for a second before we would run out of space, and my slipper clutch was slipping all over the place and he had to roll on his throttle to prevent wheelies.

The HV is a good setup, you just need to run a fan on the motor to help keep the temps down (its a high RPM, internally 380 sized motor), and solder on extra capacitors (I put on two extra for a total of three) - they really helped with throttle response and torque. If you want, check the GorillaMaxx forum and you will find my Revo threads.