without doing any calculations, my experience was, that I switched one lense wider - so I used the 90 for what was my 110 before, the 65 for the 90,... and sold my 250 ;-)
If you need some stuff, I still got the 90, 65 and 180, one RZ ProII Body + Winder, 2 Filmmags, release cable and the original Leaf adapter from H to RZ (incl. screen and cables) for sale.
cheers,
Marcel