I hope that this experimenting will ultimately produce a technique that will allow me to have consistent results. But not yet. So, meanwhile I have been printing transparencies while staying within the RA4 process completely. I do this by enlarging the transparency onto RA4 paper through a mask and processing the print. I then contact print the enlargement once again onto RA4 paper and process it. I have had better results doing this than using the b&w developer step. Doesn't take very long either.
So you use the same filtration for both steps? or do you change? and any problems with backprint?