suck it and see is the real answer
I don't have that exact same motor I think in my ics's
but motors can really vary in their output in torque and speed
so its very hard to give a 101% answer of what you exact rof will be
(especially as I use just 7.4v lipo's now)
some torque motors are only about the same as good stock ferrite's
others though can run at nearly 50% faster than a stock pulling much more beefier setups/springs/gears
so you could hit 16rps or 24 rps on just 7.4v - a massive range on stock 18:1 gears
(think your ics hits 16-ish, a bit faster than lame G&G motors)
chuck in a 33% ratio increase + a boost in volts on 9.6v and that could add on another 25-30%
if motor/battery is ok pulling spring from still on higher gears
again @ around 30rps pe "may" start to take place, could be a smidge below if piston is really heavy but think 30rps is about my area for concern
besides she will start double firing on semi @ 25rps anyway
on your ics split box - you can do aoe, seals n stuff, fit a mild beefy shs torque without stripping box right down
test volts on say 8.4v and think you will be into low 20's on stock gears without any major headaches
maybe if she is ok then perhaps step up to 9.6v but watch out for double cycling - its ok if it does slightly on a fresh full charge battery maybe
and you got AR release on ics m4's - so no worries about spring being left compressed on a slight over run when you are finished skirmishing
but it is very hard to give exact pinpoint results and yes/no to PE