Check the film base thicknesses and figure on adjusting your EI accordingly. In my experience so far with Diafine the manufacturer's suggested EIs are about right for traditional style films but anywhere from a little off to way off on thin emulsion or newer technology films like T-Max.
And I didn't like the results with T-Max films anyway.
Remember, since Diafine doesn't respond to N+/- development, the way to determine the best EI for a film is to simply bracket exposures. It works.
No stop bath or water rinse between Parts A and B. That'll kill the developer action.
Water rinse only after Part B is finished. I agitate a tankful of plain water for 30 seconds.
No indication of problems with any residual Diafine shortening the fixer life.
It's a handy developer when combined with the right film, lighting and subject matter.