[FredV]

to answer Fred before, i used both solutions with the pads and no better results from one to the other (racing and road).

Malcom,

i run no vented disc at the rear (yes i know it's a shame)
I think the calliper clearance won't allow a vented one, is there any spacer to put in ?
I am 100% sure that the odour is not from the clutch.
I ran several times the car on track days and the braking performances decreases more and more even with a pad change.
Last time at Monthléry i had what you explained: a long pedal after several corners and brakes but i thought it was due to vapor lock and i bleeded the brakes, i also removed the servos but the result was the same, excepted a stonger pedal with a better feeling on it.

My advice is that my rear brakes are not strong enogh, this car with a central engine needs to have a good balance between the font & the rear, Fred you use HiSpec callipers on the rear which might change everything in comparison to my setup.
I think this is the first way i must explore before changing all the front drive trains.
But the uneven pad wear on the front will remain an enigma ...take a look to the disc surface, strange wear isn't it ?