I wonder if you could enlarge 617 negs by placing the neg diagonally in a 4x5 enlarger, with the neg carrier slightly expanded.
Unfortunately not. The diagonal dimension of a 5x4 frame is 162mm so it is a bit short plus it will crop the corners off. However some enlargers, like my DeVere 54 have a larger light source/diffuser than 5x4 so could be adapted.
"People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.