C3 has a straight post for the XM.
Keep in mind the XM is already much farther forward than the Cat or Polaris already.
After getting used to the Doo style steering ( and riding style that goes with it) I prefer it to the vertical...and I rode a M-Cat for a couple years and loved it. I find more advantages to the slightly layed back post than I do with the vertical...keeps the bars closer to the rider, not forcing the rider forward as far to "reach" when bars are turned. JMO-
That being said, I have spoken with several people who have gone to the forward post and like the results, others didn't notice any advantage ....It comes down to personal preference I suppose.
Well... Where the post comes out, IS further forward than cat & poo, but if you run the riser inline with the post like you mention, you're actually further back than on a cat anyhow. I'll have a 4-6" adjustable riser on it, (likely set at about 4.5 from what I can tell) which will move me forward some, but anything I can do to get the post more linear, and more vertical I can't see being a bad thing for me anyhow. I very much prefer the post in line, but I like the riding position, with it more vertical, I'm hoping this accomplishes this.
I plan to put the riser I want on first & see of that, when set up properly for me gets me where I want to be. Who knows, maybe that will feel like the sweet spot for me.
The other question though, if I were to do the kit, and NOT like it, could I keep their post in, or is there not room for that?