Thanks for the thoughts. The tandem creates complications. As I observed this morning, the non-drive side is also a drive side as it contains a chainring that connects to the captain’s chainring. Both sides appear to be made similarly, with the crank arm somehow riveted to the chainring.
Looks like I have two options.
Option One - complicated and expensive, and probably won't work - find suitable sized tandem chainrings for both sides that have removable crank arms, then find shorter crank arms. The problem here is that both the left and right side will need spiders to be able to attach to the chainring, and with the left and right threading, that will likely be impossible to find in the shorter size crank arms I am looking for.
Option two - relatively easy and inexpensive - as suggested above (thanks Bill Kapaun), drill a second pedal hole on each crank arm, and tap the hole to accept a 9/16-20 pedal. I will need a right and left tap. Luckily Park Tool (picture below) sells a left and right tap set (
Park Tool 9/16-20 pedal taps, click here), and they suggest a 33/64 drill bit for the hole. One of the comments on Amazon for the tap set says this is for chasing, not for creating new threads in a smooth hole, but I am going to give it a shot. Not sure why Park Tool would recommend the drill bit size if these weren’t suitable for creating new threads in a smooth hole (I am going to email Park Tool about this). Worst result is it doesn’t work but I have made my bike a little lighter. By the way, Sheldon Brown has a great write-up on taps
here. Thanks again.
