More new tools! Maybe this is part of why I like building planes.
I noticed that the Dynon ammeter shunt has 1/4″ holes. I hate to use 1/4″ bolts to hold the shunt to the firewall, because of the wasted weight and expense. 3/16″ bolts are overkill too, but at least I can use clip nuts that I have on hand. I cut off two short lengths of aluminum tubing to use as spacers. This is a handy size of tubing to have around! These pieces were leftovers from the Vans battery box kit, but I’m planning to order another foot with my next Aircraft Spruce order.
It took a little bit of trial end error to get the length right, since too long of a tube piece would allow the shunt to move out from the firewall.
After studying Z13/8 and the firewall, this is the best layout that I could come up with.