I had a Blue Pig X which simply would not hold a Reverb in place without stopping the seat post return. I sent it back (the frame) and got a full refund.
I really don’t know wht it wouldn’t hold it. Very thin steel walls in the seat tube, external seatpost shim to fit a clamp? I tried a Thomson, Nukeproof and Hope seat clamp none worked. Even after degreasing the frame and seatpost and adding a tube full of carbon paste…
Swapped to a Carbon 456 and no problem.
C