Re the Progressor 900s, go here:
I skied on my new 2015 P900s 9 days this season. I liked them a lot. The factory tune wasn't bad, but after a really good pre-season pro tune, I expect I'll like them even more next season.
I'm 66, 5'7" (170 cm) tall, and weigh 170 lbs. I got them in 170 cm. Bindings are mounted at the factory standard position. I ski in New England. My favorite terrain is what I call 'easy blacks' - steep but more-or-less groomed. I guess I'm a low Level 8 - great on anything smooth and firm; just OK in more 3D stuff.
These are not race skis - they have a race-like feel but are not as demanding and have a wider performance envelope. They love hardpack, even ice, but they don't mind a few inches of fresh, cut-up, or wet spring snow. They're happy to go slow if that's what you want, but they love to go fast. They're not nervous, but they do prefer to be on edge most of the time. The tips really pull you into a turn; the tails are firm but don't toss you around. They have a fairly traditional feel, albeit with a hybrid GS/SL character: at head hight, they feel like a very quick GS ski; I think at 5 cm shorter they might feel more like a relaxed SL ski. But the progressive sidecut allows you to vary the turn shape easily. Coming from a succession of longer stiffer citizen GS skis, it was a small step down in top-end performance with a big gain in ease-of-use, quickness, and versatility.
So, I think they're a lot of fun as a mostly on-piste high-performance carver for an aspiring or ex-expert! I was thinking of adding a 2nd ski to my arsenal, but I'm now leaning toward just keeping the P900s as a one-ski-quiver until I'm 70 or so, when I might go a notch or two wider, shorter, and/or softer. However, in the OP's case, at a 75 mm waist, I wonder if they'd be different enough in comparison to the FX 84's. Maybe a slightly narrower but not-too-aggressive SL ski (don't personally know what that might be) might be a better match?