I've had first hand feedback from some people who eventually had leaks and MC problems with DOT fluid in the mineral oil only clutch, and a lot of people said 'don't do it', including my dealer, so I didn't. I suppose you could do it. You did it before. *shrug*
As for the 390, I am betting it is the same clutch. It has the a different crank, rod, piston/cylinder, different ECU/EFI mappings, and *maybe* different size valves and/or cam grind. Beyond that, I am betting almost every other bit of the engine is the same.
Rekluse will probably get back to your soon.
I like my LHRB and I use it most of the time instead of the pedal. I think it gives me a bit more feel, and I don't need to go looking for the pedal in tough sections. The new Hussys have a very strong rear brake - I had to put some air in the line to make it softer.
Worst case, you can use both pedal and lever to apply more pressure, but I have never had to - although I sometimes do out of reflex/habit.
You'll love the Rekluse. You've had an auto-clutch before so you know how good they are, but everyone who has ridden my bike called it a 'tractor' (I have 12/52 gearing) and liked the clutch. I lowered the idle to just above where the bike would struggle to remain running in gear, then had the Rekluse installed and set to engage medium hard about 200 to 400 RPM above idle. Now the clutch remains engaged while idling along on the trail until I come to a complete stop. So I always have engine braking unless I stop the bike to let the engine idle down. IMO this is the best of all worlds.
The only thing I wish is that I could bump or kick start the bike, but I have had no battery or starter problems yet and I hope I never do.