Been thinking about producing fine negatives and wondered if anyone knows
what effect the concentration of the fixer has on image quality.

Would for instance a more dillute fixer used for a longer time be less agressive and perhaps improve edge sharpness ?

I use Hypam at the recomended 1+4 and make it up fresh for each film.
at 20 c I give it 3 mins...ther fixer is then used up in the print baths.

I know you will say just try it and I will

But it would be silly not to ask the world if they have been there already.