I have to question the “if your running setback/layback seatpost the frame is probably the wrong size for you” response that seems to be a STW favourite. The Setback/layback of a seatpost should have nothing to do with getting the right distance to the bars, yes people do, do this but it doesn’t automatically mean, when you read they they need a setback post, that they are on the wrong size of bike.
I would like to see these people argue with 99% of the pro road peleton or a very large proportion of the world cup xc racers that they are on the wrong size of bike. Would you tell Jaroslav kulhavy or Abslon or Cadel Evans they they are riding the wrong size of bike?
I run a setback post and the saddle set fairly far back on the rails because I have long femurs and need it far back to be in the right position, and this is no me just deciding this but clearly confirmed by professional bike fitting.
Also as the OP has used 350 post, as the SLK one is, it’s unlikely that he’s too big for the bike, assuming that he did not run it above the max extension line.
Aaaaaaaaaaaaauuuuuuuuuuuuuugggggggghhhhhhhhhh sorry for the rant but it really annoys me this stock responce because it make little sense or certainly is not a definite answer you can throw out there with out seeing the guy/girl on the bike or at least the bike it’s self.
As for posts, yup thomson is probably your best bet.