PC800 comfortable cruising @ 90mph?
Speaking as one of the older boomers, and by nature a somewhat cautious rider, I don't think I'd feel comfortable "cruising" at 90 on any bike.
Life's too short to go that fast.
I know there are PC800 owners who have done Iron Butt rides, but that's not my thing.
I felt comfortable at 70, got up to 80 for stretches when I had distance to make on the interstate and was feeling alert under good conditions.
You could get more responses from the Internet Pacific Coast Riders Club group.
"Polar Cruiser" - 1990 Honda PC800 72k
2002 BMW K1200LT & Kompact Kamp trl