[PeterB]

in the contact frame emulsion side to emulsion side with another rc paper and exposed it thru the "neg" paper onto the new one

How does the sharpness of the positive compare to the original negative ? Could you check it out with a loupe for us if it there is no obvious difference ?

I realise the emulsions are quite thin (perhaps 10-15um), but there would also probably be some supercoating/anti-scratch layer on top of that too. I guess due to diffraction the positive can never be as sharp, but I wonder what practical results you are getting.