Depending on your filter passband (3,5,7nm) you'd be looking at somewhere between 1-5 hour subs to be read noise limited if you have 12e- RMS read noise; also depends on the exact numbers I use in the iPhone calculator
I'd say that it is the camera that is the biggest link in the chain. Focal ratio doesn't mean anything as long as you have pixel sizes to match. Mike is using 4.54 micron pixels at F/3.8, you'd have the same pixel scale with 9.55 micron pixels at F/8 (~0.8"/pixel).
Of anything however, a lower read noise than the KAF-11002 would make the biggest difference.