Twin calipers is the top quality Handbrake, it give you full braking power without any returning pressure like an inline hydro set-up. Twin caliper bracket are easy to install and low cost. You can use junkyard or rebuilt oem caliper to fit directly to your car for a good and reliable hydraulic handbrake. For the Hydraulic master cylinder now, I suggest the smaller sized available ( 0,625in bore ) or 0,750in bore maximum. You don't need big bore size simply because its only a hydraulic displacement question. You need big pressure not big displacement in hydraulic handbrake system.