hi rexxo.I have been down this exact road on and off all this year.the HV only seems to like two pack 4 or 6 s batteries in a two plug four wire setup,on 3s one plug two wire you over heat the internal BEC fairly quickly and it shuts down like its in thermal shutoff mode. Novack claims if you install an external switching BEC it will fix this shortcoming,unfortunatly in my set up after the BEC (installtion checked by Bob N. himself at the track)it would only Cog!So now my HV is alive and well in my1/8 scale buggy 4s ,HV, 7.5 and it hasnt missed a beat.As to your .5 an MM or MMpro is the way to go. the mm pro will run your 5.5 HV motor but i cant see it doing anything well except breaking and wearing out parts at an astonishing rate,although speed run should be entertaining.When i was running Novack/3s/7.5 combo it was very drivable at 90% throttle EPA and worked well until it started shutting down as mentioned.I run an RCM chassis w/1/10 truck sized tires so im running MM/3s/36-60-3100.I strongly recomend you consider an MM/MMpro with a controlable KV motor from mamba it will save you money start to finish