Which carbon rim pads would you recommend that could fit the delta brake pad holders?
And the bigger question - would you actually ride the delta brakes with carbon rims??
The delta brakes performance on aluminum rims is sub-par compared to today's standards. I would imagine that it would be worse on carbon rims.

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You need to change the brake pad holder. Modern Campagnolo brake pad holders fit, but I think other types work too. Use any pad the rim manufacturer recommends AND fit the pad holder. The only problem I can see is that the Deltas require narrow rim width for better pull ratio (leverige?) and modern rims (ZIPP, HED) are too wide. I use Shimano AX with an old Taiwanese carbon wheelset, the rim is narrow, the leverige is fine. As a sidenote, Shimano AX has integral brake pad holder, so I had to sculpture the carbon brake pads to fit.