For the middle walkway base, it was (iirc), reac under opposite ledge (on the tunnel side), arm across the middle until late S2, or against wall, or in opposite alcove/nacelle/space-under-default-base-ledge.
This was with some players who were also adequate solo and group rushers, killers, and base-destroyers (iirc, it was Anthony & Ryan), and they were able to keep the enemy at bay as well as keep a press on their base pretty continuously. It seemed like a strategy for a player who expects to be constantly confronting the enemy, changing loadouts, repairing & rebuilding, and rushing again (and they also had the required binds, so they could switch from nadesaw to repairboy and back to flamesuit with the necessary quickness). The enemy usually stayed default, although they often went to the middle building or tried to build us in.

Just wondered if you had tried/seen/attacked/defended such a setup (games were usually in the 3v3 to 6v6 range, when they tried this move).