I just watched a guy running 12s in a 1/5 outcast, for nearly 2 hours straight, 3 sets of packs, all on Qs8's and the connectors never even got warm, let alone catch on fire.
My comment was in reference to the 8s platform. At 12s, the car would destroy itself long before it could catch fire. 12s wouldn't make much of a difference to the connectors anyway since the esc and motor are depicting the current flow, not the connector or the battery so I'm confused as to...
It's completely fine to do as you intend. I wouldn't want to risk running Ec5's either as their current rating is much lower than Qs8's. That's what I run on all my 8s stuff. I would also suggest getting the V2 Qs8 anti-spark. Good stuff.