If you look in the book (you do have the book, right?) Bob details the primary FOT on the back of the firewall, as others describe (for all the higher current, noisy ground returns), and an avionics ground bus near the instrument panel. In that case, the avionics ground would have its ground wire run back to the firewall.
If you're grounding everything at the instrument panel, then 'float' the FOT & run a heavy ground wire(s) back to your firewall ground feedthrough. The whole idea is to keep your avionics grounds away from a situation where they are 'between' other items' ground connections and the battery negative.
BTW, if you're using high quality PIDG terminals, the shrink wrap is redundant. Looks pretty, though. :-)