I use 285mm discs with single pot callipers on my 205 (Gti-6 brakes). and i'd hazard a guess that it weighs the same or less than your puma..

with track day pads in, they might take a few corners or a lap to heat up.. but when they are, they are VERY good.. the advantage of bigger brakes is the resistance to fade..

TBH mate, i'd look MORE closely at your choice of calliper from the point of view of
the PAD CONTACT AREA.. thats why i see results with mine IMHO, because the discs aint that big really, but the pad contact area is HUGE.