On my rally i30 we have 4 spot AP calipers and DBA Slotted NF sonata discs. originally we had SBS brake pads but have changed to Pagids. The Discs needed to be machined down in diametre because we run 15inch wheels on dirt and had trouble fitting the rims over the brakes. Wheels are Braids. On the Rear they are Standard Discs and Calipers with SBS pads.
At Targa in 2011 we started with new pads and discs on the front and they lasted the week out which I thought was pretty good.
When we first started competing in the i30 back in 2010 the brake balance front to rear was not that great, the fronts kept wanting to push (understeer) and we looked at caliper upgrades using OEM calipers but had no luck finding ones that would just bolt up to the std caliper spacing. we were going to look at changing piston diametres for the std rear calipers also but never got far down that road. in the end the change to Pagids fixed the issues we were having with the fronts.
Kevin Gavin from Specialised Brake and Clutch in Penrith NSW did our brake conversion including ADR braided hoses.
Cheers Mick