I have been trying to find out more on this subject too. I have an 09 Stumpy Pro and I have got a RP23 7.5 x 2 from a friend. With some new bushes I have just fitted it on my bike.
From a mechanical side there appears to be no issues with rubbing or contact throughout the entire stroke. Also, as my bike has a 140mm Talas fork I don't see that there is any major change to the head angle compared to running in 120mm setting on the Fork with the standard brain shock. So the end result is a higher BB (8mm ish - good thing) and around 15mm extra travel.
My question is, now I am trying to get the settings right does any one know what compression and re-bound tune will work best (I am around 85kg with kit) and anyone got any tip? Is the 09 suspension a rising/falling rate? I will probably buy my own RP23 now that it seems to work ok, so I want to save time going round in circles to find the best settings - also need to chose whether to buy from ebay or new.