The alleged RCS is .5m^2. I.e. it's quite a bit more noticeable then the F-22 or even F-35. The question is what it has in regards to sensors (talk of a new OLS that's distributed along multiple parts of the airframe), data-link, data-processing, etc. The other major question is whether the VVS will be able to structural accomodate an advanced fighter jet in regards to integration, weapon systems, etc. All of this will have a much greater bearing on the success and effectiveness of the PAK-FA then the difference in RCS between it and rival 5th generation fighters which it will probably not face in combat for decades.
I'm not sure which 50hr MiG you're referring to, but RSK MiG had a 15% stake in the project so they certainly participated in the development process. The MiG 1.44/1.42 was certainly taken into consideration. YaK on the other hand pulled out of the project at some point (I'm not sure exactly where).