I’d use RR on a road bike.

Yeah, do it – it’s good !

I want 10 speed flapy paddle snifters, only reason im still on 9 speed.

Ultegra flat bar 10sp lever works fine 😀 (Oh, hang on – you mean flappy brake levers ? (dual control ?))

Is rapid rise the one where you can’t brake and down change at the same time?

No, that’s dyspraxia

Talk me through the process.

[edited, didn’t read intervening comments]

I want the same rapid rise I had when I was 16 🙂

Talk me through the process.

The spring on the mech pulls it the other way – ie lower gear ratio not higher gear at the rear.
I use standard shimano shifters – just the rear shifter now works ‘other way round’.
They shift down gear (as you start to go uphill) more ‘naturally’ as the spring ‘waits’ for you to just ease off pedal power a smidge and shifts quickly without cable drag to slow it. <- that is noticeably better.

MOAB, I think fourbanger’s suggesting you can’t trigger the downshift while your finger’s busy braking

… unless you use your thumb

Braking is what this finger is for:

I think fourbanger was suggesting that you cannot brake and shift with a flappy paddle brake shifter….

Braking is what this finger is for:

😯 – that’s just willful weirdness, so I’m out !