One has to wonder if massive brakes really make a difference... I have a couple of sets of discs im doing and im going to get the plates cut, so to standardise im going to do all the discs to fit 10", ie 7.9"....
Facts:
A set of S discs in good order, with decent pads are great... Only reason all these brake conversions are being done as we all probably know is because S discs are rare and expensive, not because they are crap....
Arguments:
Hondas have more pad than the S discs (and i reckon the S discs have more pad than the metro/LS discs incidentally) and are a little bigger at 7.9 and a little thicker, which is nice. They should be simular to S discs, if not better, and they should run a bit cooler. However the 7.9 inch conversion is a lot more work than the 9 inch conversion
People i know with the 9 inch discs arent complaining, they reckon they have great brakes, one of our "carclub" members even has a booster on the 9 inch discs, cos he had one on his drums prior to the conversion (probly put there to "fix" tired/worn drums)
But one has to wonder if 9 inch civic's and moreso the ventilated accord brakes and other massive brake conversions are a bit of an overkill, infact it could even bee a little dangerous, brakes could run cooler than optimum running temperature for the pads, making them less effective, but more concerning is i reckon these brakes could work TOO well.... Ill explain for any who arent following...
Conclusion:
Good braking isn't neccecarily the ability to lock up easily, this isn't the fastest way to stop (not to mention being hard on tyres!), the fastest way to stop is to depress your foot as much as you can WITHOUT locking up the brakes and sliding, if you lock up you should back of and re apply the brakes technically for the best braking....
Another misconception about boosters, they dont make braking better, they make braking easier for the driver, just another thing to go wrong, heh... More feel without anyway..
The S discs on my car are pretty tired and thin and they stop on a dime, and i can lock the wheels up relatively easily without a booster. When one gets into trouble on the road you generally will depress your brakes very hard, unless your as cool as Bond, if from nothing else but adrenalin, if your brakes are too good they will grab hard and youll be off and sliding
Maybe the increase is size and power will be offset by the decrease in heat.. who knows
I don't want to take anything away from the big brake conversions, the ventilated discs on this page look awesome! (a lot better than the pictured cars brake hoses...

) and are great pieces of engineering, but those big discs willl lock the front of a mini up very easily if rapidly depressed and unless you know how to control your brakes you might get into some trouble.... trouble you might not have got into even with a half decent set of drums, that would be ironic!
Spose if you do have big brakes or are set on them, make sure you practise some emergency stops to get your technique down, certainly wouldn't bother with a booster, i'd even unfit one that was there if it was my car as i think feel would be extra important with these big brakes
Just thoughts, speculations and hypothesese.........
G