As Chris mentioned they are PBR calipers and I think a similar caliper was used on the fronts of C4s if I'm not mistaken.
I think this is the OEM sales sheet on those:
http://www.pbr.com.au/downloads/broc...r_Brochure.pdf
I imagine some discussion with PBR directly would result in some insight to the problem if it is indeed non-cooling related. I know that these same calipers are used on the front of Australian Roaring Forties GT40 replicas of which a few are used in sanctioned racing there. I know one of the guys really well and I don't recall them indicating they had caliper flex or failures, but I'll quiz him more directly about that.
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