Chris, my TR 11.0 will plane at least 2 knots earlier than my 9.2. If I go out in 5-12 knot winds (typical summer winds in Dallas, Texas), I will be planing 80% of the time. If I use my 9.2, planing would be cut to probably 40% of the time.
I have a sailing buddy that weighs about 25 pounds more than me and we are pretty evenly matched speed wise with him on his TR 10.0 and me on my 9.2. However, I can still pump on plane quicker than him. The point being, if you weigh a lot, you need the largest sail the board can manage with good balance for light winds. In your case, the 11.0 will give you a little edge over a 10.0 for early planing. You should also be able to handle an 11.0 up to about 16-18 knots with a little practice.
I am also talking formula race sails that have a much greater range on the top end than freeride sails, especially if you have an adjustable outhaul.
I have recorded all of my outings on a GPS for the last 4.5 years. Here is one from last summer:
Top Speed knots: 25.5
Average speed knots: 10
Distance sailed: 12 miles
Time sailed: 70 minutes
Winds speed knots: 4-16
Sail used: TR 11.0
Board: Formula 160
Formula 160; iSonic 111; HiFly Move 105; Tiga 263; '85 Mistral Superlight.
Maui Sails TR 11.0; 9.2; 8.4; 7.6; 6.6; Maui Sails Switch 6.0; 5.2; Maui Sails Global 4.5; 4.0.