I did that segment! Well, plus some. When I was in Pittsburgh visiting my parents a year and a half ago I figured I'd try hiking the LHHT from SR653 to Ohiopyle- about 19 miles. I figured I'd make an over-nighter of it, so I had breakfast with Mom before the drive out from the city, hit Falling Water since I'd never been there, and I finally kicked off around 11:00. Well, I had thought that I was taking my time but I ended up strolling into town around 20:00, even stopping for a leisurely lunch and doing a lot of gunking around the rocks. I'm sure that it helped that it was a significant net-downhill.
It was quite a pleasant late-summer day, no bugs, I only saw one other human being on the trail, and it's an area that I love for quite nostalgic reasons. I used to poke around Ohiopyle a lot as a kid and nearly killed myself rafting it on several occasions long before the outfitters swarmed the place.
The next time I'm back visiting the parents I think I'll take a couple of days to circumnavigate Black Moshannon park.
(By the way, I'm a Pitt alum, too...)