Ok, so you just soften the edge a little with a little radiusing, I would just rotate the file while I stroke it lightly, just a stroke or three!

I agree, we are worried here about the saddle rail, not the seatpost. I also use a lot of setback, probably for the same reason, to keep the weight off my hands when in a tuck. Somehow my pedaling has adapted to this oddball position, and despite the efforts of the new bike industry my body is not changing it's mind.

I'm still trying to be able to pedal well enough to fly off to somewhere else!

I have a Selle AnAtomica carbon saddle still waiting to be tried out - I'm sure this will also help out its carbon rails!