The clutch performs fine with more power. There is a local guy running 4s and a 1515/1.5D with no clutch issues. I've run the clutch setup in buggies and truggies on 4s with no issues. It runs in the Revo on 4s with no issues. I'm sure it will work fine with 5s or 6s. Not sure why we're talking about clutches again, they hold up fine with .28 and .30 engines in nitro vehicles.
3s locked in 1st is what I'm currently running and it's not quite fast enough. 3s with the 2-speed is much faster and compares favorably to a nitro Revo. 4s and a 2000+ kv motor will put any nitro Revo to shame. In my experience, the 3s setup is a good track setup with plenty of power and great driveability which is why I've run it that way for so long, I don't bash.