Have you looked at different compounds of friction materiel? the likes of willwood and AP offer a verity of pad compound to fit 1 caliper type and the difference is remarkable I have no idea of the availability for standard calipers but softer pads tend to bite harder there for stop quicker.
what options are available for hgt owners does anyone know??
I would be very interested to know what other calipers you can fit on the rears as the standard lucas calipers are just not up to the job at times