No idea. I've never ran them. I looked that the FAQ and it looks like gimmiky horseshit to me. According to them the valve only helps tune the top end and effects nothing else... Your discription sounds more like an automotive power valve (IE enrichment circuit).
That's not how bike carbs work. Plus who cars if you can run a smaller main? I've never hard of bench racing with main jet size much less wanting a small one! Top end fueling is a factor of jet size and needle thickness anyways. Plus the only time you're full main is at full honk.
Unlike a Holley, on bike carbs the main jet is the refrence point everything else revolves around. You set the main for maxxx power first. Then put the needle, spring (if CV) and idle circuit around it.
Plus those RZ's are almost idiot proof when tuning. If the tune is 80% the power will still be pretty close to spot on.