Thanks for the link. I've not heard of XXCycle. Are they US (or UK)? If not US it seems like shipping would be long & expensive. I assume that the standard small ring BCD is 74mm (not the 72mm I stated above).
I'll have to look at our setup this weekend. I recall that our chainring setup is as stated above but I need to verify.
Actually, shifting up & down in the front is fine - its just that the drop from bike to small in front is huge and I was trying to reduce the jump in front to a more incremental step in the rear. On my single bike I can pretty easily pedal up to about 18 mph on the small ring (39t). On our tandem, we pretty much run out of cadence about 15 mph on the small ring (34t).