StopTech seems to think monoblock calipers are worse than 2-piece calipers bolted together with steel bolts.
Wilwood says the same thing:
Q: Which is the more ridged Caliper, a two-piece or a monobloc?
A: Everything being equal, a properly designed two-piece caliper will flex less than a monobloc caliper. Stiffness is a function of the material’s modulus of elasticity. Steel bolts have an elastic modulus approximately three times that of aluminum bridges. There are some exotic aluminum alloys that were developed for F-1 racing that have almost the same elastic modulus as steel; however, they are expensive and not normally seen in after market brake kits. Steel has the added benefit of not losing its elastic modulus as things heat up. As a matter of fact, steel’s elastic modulus actually increases in stiffness as temperatures rise above 200 degrees F by approximately 30 percent, where it stabilizes at 400 degrees F. Aluminum on the other hand, loses approximately 50 percent of its stiffness by 300 degrees F.
Very few high end calipers are monoblock these days... interesting that the PFC one is. Definitely report back how these work.