OK here is the thing if the above is true and brake pressure ratio is caliper to m/c piston ratio , you have to take into account the fact that the front 23mm piston is pushing a 19mm back piston hydralicaly in the master cylinder .In the calculation this gives a ratio of 1.9 on area guess what the equivelent areas are now 23.8 is 444 and the 19.05 is 443 so if the 23 is nearest the driver it will supply more fluide but not effect the bias at all ie harder pedel on 944 na calipers , maybe this is the reason some people swear 23 on the rear is better and some 23 on the front is better , it seems strange that porsche picked these two bore sizes that when area is calculated as a ratio of each other give the same surface area , could anybody chime in that has infact run the m/c both ways , i would be interested to hear your results and if they match with my calculations .I rang a brake specialist(allegedly) and due to the fact split bores are not that common he could not give me a definative answer , infact no answer
cheers jon