Transponder.

WC... I have found that as long as you have a peak window below the TP, you can place it on top of carbon. No peakaboo and yeah, you have possible missed laps. I have my TP placed on carbon on both my SC and buggy but there is some of the transponder over a cutout in the carbon on both. Just a little window will do ya.
Or like you said on the servo, that is high enough above the carbon that the loop can pick up the TP.