The F3 is the 6-34573 from 2010.
Your stl printed just fine with PETG at 0.1mm layer height... and, 1 minute to print.
I just ordered the Nylon, we will see how that goes as I've not used it before... and, then of course I have to sit down and actually do the install. So, maybe 4-5 days.
Is that tiny darkish spec in the middle of the platen the spider?? Good to hear it printed well. I suspect that to fit it to the motor shaft you are going to have to ream out the center hole somewhat. A 2.3 bit in a pin vise seems to work well. I just happened to have that exact size bit in a set of metric drill bits bought a while ago. You could probably find a bit close enough in a number bit drill set too; like a #43 or #42. It will be interesting to hear how it fits up for you. BTW, you probably know this, but you can easily remove the truck from these engines without any need to take it all apart. Simply turn the truck about 110 degrees CCW. Then hold the engine right side up and lower the truck away. There is a 3 pin plug to easily disconnect the truck from the engine.
Your SF F3's are in the same era as my CP F3's; they are 6-34582. Do you run the F3's tail to tail? If so you likely have found that both headlights are on in forward and off in reverse. And that you need to hit the F uncoupler to open the coupler on the rear dummy unit. And that the backup light is lit on the rear dummy unit when both are moving forward. It's like Lionel wired them up so as to run both nose forward. But if you run them this way then the electro-coupler on the rear dummy unit is on the front connected to the front unit; which makes no sense at all.
I made a couple of minor plug n' play wiring changes on the dummy unit so it now plays well with the front powered unit. The rear coupler now works when you press the R button, the rear headlight is on in reverse, off in forward, and rear marker leds are red when in forward, and the backup light is off when it should be. Cab lights are off in motion and on when stopped. Way more sensible. I can show you exactly how to make the necessary changes if you like. Pretty simple, no wiring changes and no soldering. No changes to any OEM parts at all.
Rod