Synchronized Sony a7r / a7s cameras

I'm cobbling together a synchronized shutter-release / timelapse controller for triggering Sony a7 series cameras, and it seems to work! Although, as is usual when chaining remote cables together, I'm observing some strange behavior. For example, when I connected only a 2.5" to Sony Multi-Terminal cable plus a 2.5" to 3.5" cable adapter, all physical controls on the Sony camera disabled themselves (but I was able to trigger the camera via remote). Moving to a wired Satechi remote from a wireless Neewer remote seemed to free up physical controls, although I haven't done exhaustive testing. Still, the proof of concept is sound, and I'm going to order the remaining cables to get 4 cameras synchronized. I haven't tested how accurate the sync is (yet), but I'm targeting long-exposure timelapse, so having extremely accurate sync isn't required.