Royce hubs

... thought that you use two chainrings at the front for dingles?
Same chain length for 2 different ratios in the same dropouts.

With a 17/19t Dingle on the back, pick two chainrings that are 2 teeth apart, like a 44t and a 42t. When you change from the outer (44:17t) gear combo to the inner (42:19t), you’ll have a much better off-road gear and your wheel position will not change.