ABS & Proportioning Valve Question

[Bob_n_Cincy]

To all the smarter than me people who have posted many interesting discussion relating to 818 and ABS. My chassis (131 RHD) is currently onboard an ocean liner expected to arrive 37 degrees below (New Zealand) soon. I'm definitely not really smart enough to post here - however I am definitely going to include ABS in my 818S, and I have been studying everything anyone posts about ABS and researching elsewhere for what I trust is hopefully a full proof plan for success.
My limited experience with Mid/rear engine vehicles was some time ago with both Fiat X19 and Carrera 3.6. Both these vehicle's I liken to the layout of an 818 with an engine adding significant weight/traction over the rear axle when compared to any standard front engine rear drive car. Both these cars have the same size callipers and disks on the front as the rear - so with the foot hard on the pedal the result is very rapid deceleration without either front or rear hinting at locking up - the Carrera certainly squats in the back and the rear wheels contribute significantly to the braking. If I compare to 90% of street/production cars including the Subaru range - they all have significant more brake force/size in the front compared to the rear.
So my 818 plan is to have stock WRX front callipers and disks, and upgrade the rear to the most significant STI callipers and disks I can (without stretching to Brembo's or WW). I would ideally like to adapt the rear to accommodate the same 4 pot front callipers - but I suspect this will be a little mores difficult to do although still an option worth looking into more.
After this logic of upping the rear - the balance should be closer with the added weight over the rear from standard. I would love it if I could get the rear to hint at locking up under very heavy braking before installing the ABS...
Part 2 is the ABS. I intend upon swapping the front LH and rear LH sensors and position from the ABS controller. Within the Subaru the diagonal distribution must have been developed to provide some brake to front and rear and RH and LH sides in the most incredibly unlikely event of 1 out of the 2 circuits within the Master Cylinder to fail. This is most likely well planned for an original WRX slowing from 40mp/h on a street with its 4wd helping to offer a little balance also. However in an 818 likely to be travelling significantly faster on the track or autocross course, in the same incredibly unlikely event 1/2 the master cylinder was to fail - I would never wish for brake force on the Front LH and Right Rear or vis versa as my only braking, as this would result in an uncontrollable 360 degree spin for sure?
So my logic/plan would suggest that in this same unlikely and unfortunate event, by swapping the circuits on one side we should theoretically retain either the front or rear as a more even stopping force? I do not intend upon needing or running any bias - increasing the rear system should suffice. I look forward to reading about someone successfully plumbing the Subaru ABS and posting their results soon.

Junty,
We are thinking very much alike.
I also want the ABS for safety reasons. Plan on having key switch to turn it off if desired.

Because of the rear weight bias and low CG, I am putting the same size calipers all around.
Here is a picture of my rears. I need to do some machining on the bracket to make it fit.
I'm using a 11.4" vented rotor and dual piston calipers in back


I haven't thought about your ABS mod yet.