I've had the opposite experiences as Cody- I would only recommend flex uppipes, as it's super easy to botch the install without it and cause a gasket to fail. He's never had an issue, but when I worked for Vishnu we had a lot of people with solid uppipes have problems, and very few with flex joints. Way back in the 20th century it wasn't uncommon for flex joints to fail, but I can't recall hearing about one happening in a really long time.
Happily, I happen to have a coated flex uppipe (pretty sure it's a Grimmspeed) that I ended up not using on my FXT if you're interested.
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FWD is the new AWD
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