Mark, Thanks for the videos, I would not say that your traversing those turnouts is slow, moderate speed yes. Hey those Marx bridges are cool, I have two on my home layout but only with single tracks.
I did do some trial runs through my first set of modified turnouts using a number of locomotives, from a Flyonel GP to a Flyonel Challenger, and rolling stock from a few freight cars to an AM streamliner coach. All went through without a hitch at a number of different speeds.
Again, Thank you
Ray