Per Ady's post.... I'm between 175-180 lbs. Windsurfing for 8 years, so I'm somewhere in the mid-intermediate to advanced-intermediate stage. I sail Lake Michigan and all the different conditions it presents. Boards are a 11'8" Exocet Windsup, 145L RRD Fireride, and 108 RRD Freestyle Wave. Also have a 94L RRD, which I haven't used yet. Like I say in another recent post, the Windsup has quickly become my most used board (which, in addition to windsurfing, also opens up options for lightwind wave-sailing, SUPing, SUPsurfing, and lightwind freestyle).
Greg, I should also mention that I have a 9.5 Ezzy Lion (cambered) sail. I got this sail to use for the FreeFormula board, which I no longer have. I can usually get the 9.5 planing on my windsup in 13+ winds. But if it's blowing 13-14 and if there are waves, I will almost always choose catching small waves on a 6.0 than sailing the 9.5. If there are no waves, then I'll go with the 9.5.
If you want to make the 8.5 the biggest sail in your quiver, I think that the cams are a good idea. The cams may give you 1-2 more mph on the sail. For me, at 175-180 lbs, I take the 8.5 Freeride sail out in 15-16 mph conditions, and my 7.0 in 17-19 mph conditions. (That being said, there are times when the wind has picked up and I've used these sails 5 mph beyond what they're usually intended for. Not optimal or easy, but still doable.) I really have no issues going from an 8.5 to a 7.0. For me, anything in between would be a bit redundant. For another perspective on quiver sizes, check out this windsurfing
calculator. You'll need to figure a little extra weight for harness, wetsuit, PFD, etc. when putting in your weight. Enjoy the Ezzys. They are durable and consistent. (You can also e-mail Ezzy directly to inquire about how the mix-and-match would work for your quiver.)