No not at all, remember these engine mounts were made for the RB20 onto this chassis, they wouldnt have released it if it wasnt safe and although the 25 is a different engine and I do have a lot more power than stock, it was over engineered (if theres such a thing) and I havent had a problem at all and have checked the mounts and chassis area of it all and there isnt a problem.
At the moment, I reckon if your going to do an RB conversion, then do the RB25 because they have come down in price a lot since i did it and they are easily the best bang for buck. I know a guy with a RB20 in a 240 here in Canberra and even after some work, still had nothing on me at stock. Im pretty sure its only a 2k purchase difference cost between them.
end rant