Conv question

currently running a Coan super mega 10 1/2" conv (half steel half billet)

Going to try a Coan super mega 10" (all billet)

Same front pump, same stator etc etc. just the diff of 265mm to the 258mm

Wilh all that being the same has anyone ever backed to back or switched ? If so how much looser was the 10" vs the 10 1/2??