I am currently building a bike for my wife and have run into a problem with the rear wheel. We want to put a coaster brake on it but we are having a problem with the rear spacing. We need a 175mm axle for the hub and I cannot find a prebuilt wheelset that has that. I have found some replacement axles that length and I am thinking of switching them out. I have never messed with anything involving hubs. Would I be opening a huge can of worms or can it be done relatively easy?