beachedbeluga,
I got the fit report you sent and I scoured it - this looks logical to me and I'm thrilled to see 165 cranks. There's lots of good looking numbers here: 91mm drop off of 760 seat height, set back of 67mm on a Sitero (hmm okay, probably). So, we're workin' with Pad Y of 685 and Pad X of 502 (Pad X is 452 but that's to the back of the pad and it's safe to assume Pad X to center is +50mm).
If you were to ride the Canyon Speedmax SLX you would need to get a size Large. The short stem that comes stock is perfect for you and pads would be mounted all the way back. Your Pad Y of 685 is the max Pad Y of this bike and you'd need all of the spacers that come with the bike AND a little aftermarket item that Canyon sells called the "high stack flat spring". Now, if perhaps, that the fit you had leaned just a bit towards numbers and less towards rider feedback, or aschewed forward experimentation (one that could have resulted in a setback of 57 or 52, etc). Then I would bet that your Pad X is more like 510 or 515...and your Pad Y would then be more like 677 or 672. The idea here is that you're position is being rotated around the bottom bracket and you get more forward in your position and lower. So the point is this - if you have to have SLX and if these numbers are good then it's a Large, short stem, spacers maxed and you've got room to move forward and down if you so choose.
If you'd like to have the ability to move up - by this I mean your drop of 91mm already seems low to you and in a few years you'd like it to be 85mm or 80mm then you should be a Canyon Speedmax CF in size Large with the 90mm stem that come stock and you're right in the sweet spot of that bike so you can move higher, lower, nearer, farther with no trouble at all.
Ian
Ian Murray
http://www.TriathlonTrainingSeries.com I like the pursuit of mastery
Twitter - @TriCoachIan