I enjoyed this route and the history behind it. I spent quite a while in the Allegheny Portage Railroad National Historic Park Visitor's Center earlier in the day. Definitely worth checking out and roaming the grounds before or after your run.
I did start too late in the day, and it ended up getting quite dark early on the return of the round-trip effort. Luckily, I remembered to bring my headlamp, which would have been disastrous if I hadn't had it. The woods are very dark, and the footing is ankle-breaking with lots of roots and rocks. It also rained heavily earlier in the day, so the course was wet and slippery.
My outbound effort on the uphill went fairly well. I ran steadily on the railroad section. I did get off-course twice on the transition from the smooth railroad section to the off-trail single track. It probably cost me 1-2 minutes total. The section through the high grass and woods is fairly technical and much slower-going, with lots of roots, rocks, and uneven footing. One-way uphill time was 1:28:23.
I had hopes of getting the round-trip FKT as well, but that got dashed fairly quickly as it got dark and my pace slowed significantly even with a headlamp. Also, I have no cartilage in my right hip, so I've had issues getting tight after 1-1.5 hours of intensity, so I ended up walking a bunch on the return, even on the smooth railroad section in the final few miles.
I carried a bladder with 1 liter of Tailwind and 3 gels. I ended up drinking about half the fluid, but did not eat any of the gels. It was fairly cool, so that was sufficient. You could refill water at the Visitor's Center midway, if necessary. I did not take any pictures.