Although why would we multiply by 17 and then divide by 14.5? Why not just multiply by 1.1724? Only kidding, doesn't matter.
I'm not exactly sure what you mean by "to scale." I mean, it's a picture, right? So, even though it's not actual size, all of the lengths should be some fraction of the real lengths. Unless I'm completely missing something, here...
As to our differing measurements, it's probably a difference in monitor size/resolution/ some-other-computer-thing-I-know-nothing-about. "Proof:" If you divide 23.99 by 19.4, you get 1.24, which is quite close to 1.17. I blame the difference in ratios on errors in measurement...or something. In any case, the difference overall would only be an added 0.22" in the length of the slide motion. And that's only good, right?
So, satisfied, Mr. Perfection? (just kidding)
And sorry, OMC, for bringing this up. I just thought that it would give us some perspective on the size of the thing. I didn't expect 3 people to post near-simultaneously with the same info.