I've heard this rumour more than once now. I did do a search but it didn't come back with much.

What is involved in getting a CBR600RR rear shock to fit a VFR/RVF?
What year CBR?
Are spring changes needed?
Has anyone got an example of a working setup they have done?

In short any RR shock between 2003 and 2005 i think, it pretty much drops straight in bar a couple of shims on the top mount. Spring is way too soft for the NC so yes a spring change and ideally the valving matched too.

I bolted one on my road bike and used it with no spring change etc and it wasnt the best, i reckon it would get out of shape fairly quick on a trackday.

oh and you need to hack the battery trap up and use the smaller of the 2 batterys used on NC's YX7 or something

I wonder if a 1000rr spring would fit/be any better?

I seem to remember reading something somewhere about removing the lower 'male' mount and replacing it with a vfr 'female' one on a remote resevoir cbr shock

I've done it twice & it aint worth the ball ache.
Fit a bmw s1000rr shock, around £140 to buy 1 & put an uprated spring on it (from demon tweeks)
Or rebuild a late spec nc30 shock for around £150-ish.