Troy
It appears that you already have an 8-position Radio Shack Terminal Strip[T-strip, or barrier strip]. If so, go buy another T-strip and a pair of 8-position plate jumpers. One strip will be used for Hot wire distribution and the other for Common.
With hacksaw or tin snips cut one of the jumpers in half, you now have two 4-position jumpers. Place both 4-position cut jumpers on the 8-position Hot T-strip under the screw heads making certain the cut jumpers do not touch each other. Connect a wire run Hot conductor from one throttle binding post["A"]to under a screw head of one of the 4-position jumpered strips. Do the same for a Hot wire to the other 4-position strip, fed from throttle["D"].
You now have 8 energized Hot screws on each of the 4-position jumpered strips fed from the two separate throttles, available to feed multiple locations on each separate track loop, either direct to center rail [or switched at toggles if desired].
With the second 8-position T-strip and 8-position plate jumper simply install the jumper as is and connect a wire run from any transformer Common [U"] post to any screw head on the 8-position strip. You have now created a "Layout Common Distribution Strip" wherein any of the 16 screw heads provides connection for a Common feed direct to the outer rails on each of the separate loops.
Hope this helps.
PS:
For example, a 6-position jumpered strip shown below with two 3-position cut jumpers dividing it. This particular one separates the Hot and Common from a PowerHouse transformer on the same 6-position strip for further distribution. 5 Hot and Common screw heads available on each jumpered side. The "thing" wired between the Hot[green screw head] and Common is a TVS[transient voltage supressor]-----ignore for now but need to consider later.
