I have a 10-speed (2x5) bike from the early '90s I've been tinkering with, and was thinking of doing a HS+G conversion. It currently has 38-48 chainrings and a 14-17-20-24-28 freewheel. I was thinking of switching to a half-step setup, using 44t middle and 48t outer chainrings, with a 24t granny gear on the inside.
Am I likely to run into any problems with this? I would set the chainline of the middle/outer chainrings as if they were a double, allowing me to use the 48/28 combo as part of the half-step setup. This would mean only really using using the 28-20 freewheel gears with the 24t chainring (24/17 would be borderline acceptable) but that places the granny gears in a neat sequence off the lower end of the half-step anyway. I'm thinking it's possible I'll run into problems getting the FD working correctly with such a big jump from small to middle chainring. Would it be better to ditch the granny gear and just go for a double?