Any thoughts or insights would be appreciated.
Thanks for writing in, I do have thoughts.
1) I am deeply suspicious of your position. The first red flag to me was your handlebar elevation (AKA drop) of 5mm. I would suspect it to be a number more like 70mm. So I have to ask myself why? Maybe your have 5 vertebrae in your lumbar or thoracic spine fused...maybe you have something of a beer belly....maybe it's something else that is special about your morphology, or maybe you're up too high- and, BTW I'm coming from a comfort first place, a power creation second place and aero for me is a 3rd priority.
So I looked at all the metrics you have offered....
2) I don't know your saddle set back or seat angle but....SX is 153 and that saddle, Fizik Mystica isn't very long so...what could the set back be..... 80mm, 70mm. Could be okay but...
My immediate suspicion is that you are not riding forward enough (hips closer to bottom bracket rather than well behind the BB) and if you were more forward then your Pad X wouldn't be 460 (to center of pad) but more like 480, 490, 500. And then your Pad Y wouldn't be 717 but more like 660.
But....let's pretend that this position is right, it is the best spot for you....your question is keep the medium or sell it and get a small. You should absolutely keep the medium and let's make that bike, your bike fit better.
Based on the info I have my recommendation are to take these steps...
First, let's talk about the primary complaint - it being a bit too long...
1) Pull the arm pads away from their velcro connection and make sure the arm cups are all the way back, as close to you as possible.
---if they are, or if when you do pull 'em back all the way the bike still feels long....then...
2) Call Canyon and purchase a 70mm stem for your CF 7.0. The one that came stock on your bike is 80mm. This will buy you another 10mm and the new Pad X will be 457mm.
Now, let's talk about that Pad Y for a sec...
The medium CF won't get up to your 717 Pad Y, it maxes out at 692 (and I don't even think you are there either - look at post #379 on page 16 of this thread), I bet your closer to 680 and that would make your drop more like 50+mm and that seems so much more logical to me.
You could also fit on a small but I think your position on a medium with a shorter stem is a better bet for you.
Get back to me with questions here and, take a look at your crank length (stamped small on inside of crank near pedal axle hole) I worry it might say 175. Let me know about that.
Ian Murray http://www.TriathlonTrainingSeries.com
I like the pursuit of mastery
Twitter - @TriCoachIan