I am not going to answer this question directly because I don't have the numbers in front of me, but I believe that CR you have been told is low. 1G's are 7.8, 2G's are 8.3 and Evo VIII/IX's are 8.8 to 1. I don't believe there is a huge difference, if any at all, in the CC size of the head but I may be wrong. To have less compression in the 2G block with a higher compression piston, on the same length rod makes no sense.
As for doing it? If you need the rebuild sure. The OEM rings for the Evo pistons are on the high side. If you have to press the piston on your rods, may as well just wait and get fully forged in my opinion. I have Evo slugs on my 1G rods and it cost me almost as much as going full forged would have. The evo rods slap onto the 2G crank though which is nice.
/brox