I second the Bushnell eccentric. I bought one after I discovered the eccentric that came with my Calfee could not work. There is no problem with using a shorter spindle on the front. I have a standard Ultegra crankset on front and a Gossamer tandem crankset on the rear. You just won't be able to use a belt drive. I would think the BB could be installed backwards, but depending on how it installs it might tend to loosen due to pedaling torque. This is not a problem if you use a newer type BB with the outboard bearings.