Pad X = 400mm
Pad Y = 667mm
Seat = 756mm
Now we're talkin'!
This paragraph is specific to a Canyon Speedmax CFR based off your numbers: Pad Y 667, Pad X 400, Seat Height 756. The right CFR for you is a size Small with the short stem (that's the one that comes stock on the bike here in the USA), with the high spacer. If your Shivs are set perfectly for you and those numbers are your optimal position.. .then that is the prescription.
This second paragraph is just me expanding on my thinking so you have more info upon which to contemplate other possibilities...
Let's say you didn't own a tri bike and all you had to give me were some basics: overall height and inseam and also what you didn't say. You didn't say "I have 4 fused vertebrae from an incident in high school where I was making out while parked across some rail road tracks", you didn't say "I'm so tight I not only can't touch my toes, I can't see my toes", you didn't say "the only saddle I can ride a leather Brooks saddle and I have to sit so far off the back of it that you can't see any part of the rear of the seat". And by not saying anything that extreme my take-away is that you're pretty normal - other than having rather long legs for a guy your height. If that's all I had to go on I would have predicted your Pad Y at 640ish and your Pad X at 460.
I don't think your optimal position is 667/400. Look at how much of an outlier you are on the graph on this chart: https://www.slowtwitch.com/...ld_Example_6852.html
Also, the Shiv is one of the shortest, tallest tri bikes out there (in some instances, like the guys who parked on the RR tracks, thank god the Shiv offers that geometry) so it kind of allows for a short tall position like 667/400 easier than any other bike.
So, here's the great news.... if you really do ride at 667/400 then the Small CFR with short stem and high spacer is right for you. If you really do ride at 640/440 - that's a small, short stem, mid spacer. If you ride at 640/460 that's a small, long stem, mid spacer. It's still a CFR size small but the front end changes.
PS. all of the above numbers, prescription, etc are the same for a Canyon Speedmax SLX.. but not the same for a Speedmax CF.
Get back to me here if I can help further.
Ian Murray http://www.TriathlonTrainingSeries.com
I like the pursuit of mastery
Twitter - @TriCoachIan