A 70 series is serious overkill in a crt.5 IMO. The 60 series would do nicely and reduce weight and should run nice and cool.
When you upgrade your electrnoics, the mmpro is the ticket for a esc.
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