Hardware/Settings in beginning, Race at 4:30.
This is the 5.57 of Grand Prix.
Though it took days as opposed to weeks, I hit 50.91 about as many times as I hit 5.61 before squeezing the last drop of time out of it. This was run after run, arm-burning effort.
Love this game, glad to move on from this particular track though!
Thanks to Greg and Nads for the help on this one-this felt great!