On 12s you will need one serious speed controller...such as....
http://www.rc-monster.com/proddetail...M90323scarboat
This one can handle up to 10s li-po.
1. MBX-6 T8 1900KV, RX8 ON 4S
2. MBX-5T 1520, MMM ON 5S
3. MBX-5 ONROAD CONVERSION 1515, MMM ON 5S
4. MRX-3 ON ROAD CONVERSION 1512, MMM ON 6S
5. TEN T 2650 T8, MMP ON 3S