Good you're enjoying it, as #2 said - that's the most important. I'd like to add a couple of things:
-1999 sail is not stone age (if it's still in one piece), I remember my North Spectros from '97-'98. They were not far behind modern day sails - proper twisting leech, stable, easily tuned, etc. I would say board design has changed more in the last ten years then sail design.
-You sail in 10/12 knots winds and you have enjoyed a few moments of planing so far. No offence, but you probably need some more experience and skill to appreciate finer points of gear choice, tuning, etc.
-8.5 shouldn't be uncomfortable or overpowering in these winds. In fact it would be close to ideal, enabling you to plane constantly (in steady 10/12 knots). From my experience, most recreational sailors choose between 8 and 9 square meters as their largest lightwind sail, UNLESS they use formula and/or they are very heavy. A 2/3 cam freerace sail of 9sq. m. will plane in about the same winds as a 5 cam 11m race sail, but it won't have up/down angles and the speed of a race sail (that's why formula guys use sails so big, not because they plane in proportionally less wind). Agree with Ken, your next step should be around 7.0-7.5.
-When you have some experience you will learn what works for you and your conditions, and you will make better more informed choices (but it takes some time and some gear testing/buying). It doesn't have to be a truckload of new expensive gear, and I won't tell you what to buy. Maybe you'll go wide/shortboard route, maybe you'll opt for a proper longboard for even lighter winds.
But I doubt you'll be content with a Rio + raf5.9 five years from now ;-)
Last edited by Screamer; 20th August 2009 at 08:09 AM.