I wrapped up a productive weekend with attachment of the major engine accessories to the firewall: oil reservoir, voltage regulator, main battery, fusebox, shunt, fuel pump assembly, gascolator, and fuel lines. This work is much easier to do before the engine is attached.
I am placing a DC contactor (basically, a high-power relay) just after the battery, rather than running thick wires up to the instrument panel through a switch, and then back to the firewall, as is suggested by the kit instructions. I designed a bracket to place this contactor on top of the Rotax fusebox, so that I don’t have to add any more penetrations to the firewall. The contactor I choose is a sealed automotive unit made by TE, designed to be used in a compartment like this. The relay will be activated by the battery master switch on the instrument panel.