Hi Vitaliiy
If you use FIXED TEXEL SIZE and use the OPTIMAL TEXEL VALUE then you get 100% Tx quality. RC is NOT stretching the UV SPACE to get mor e UVs coverage, it just give you best possible result. in external apps you can play with UVs strategy and get stretched UVs or etc( like ZBrush weight paining ). but RC goal is not do this, so results here will be always reflecting real data.