So I just thought I'd weigh in with some experiences of the changing flex positions on the '16 motor mount....
When it was a '15, I pretty much ran the team driver forward only single screw (no nut) option on the lower motor mount. Always seemed to work nicely.
Since having spoken to Olly and Alex about their ETS setups, I realised on the '16 there was a fairly decent option to change the flex by moving the screw back. I've since tested it many many times... and have come to this conclusion;
Hole 1 - Most steering, car feels like it pivots more around the centre, front feels less reactive initially
Hole 2 - Mid range steering, good compromise between 1&3. Piviots more towards rear, front has smoother turn in, but isn't too locked in in the tight stuff. This is currently my go to option for low grip outdoor asphalt.
Hole 3 - Less steering, car feels longer, and more 'locked in' on the rear. Doesn't rotate as well, but a bit smoother still than 2.
(Note, they are all without running the screw&nut, and with a 1mm raised top deck)
Combine those options with the centre post, and also locking the top deck down... the car has a load of tuning options without touching the geometry
Hopefully someone finds that useful.