You can simply go to a lower toothed pinion gear if you want to lower your head speed.
Or in most cases simply reduce the % throttle in your throttle curve. Are you using a governor?
Personally I much prefer using a governor, it just give more consistent performance and feel through the flight with no bogging down under load or as the battery gets depleted. But you could still reduce headspeed by dropping down your throttle % a bit more.
I would drop straight to the 10t and see if that's going to work. I know my head speeds are still going to be less than yours and flies just fine. Now I do know that I don't have the punch that most folks want. Pitch pumps at the bottom does not have the instant stop or crisp stop. I probably could add more pitch but for me it works for now.
Then drop straight to the 11t. I think you might find it more than enough.
Try the 11t first since you have it. I don't have the time to work out the math on the head speed. I think you will be close to what I have with the 11t. Personally I don't think you will need more than 3500 at the head. I flown as low as 2600 and did fine for flying like an airplane minus inverted.
Thanks for the info. I'm going to use is to help me out http://www.runryder.com/helicopter/gallery/32055/hdspeed.html Your right. No need to go more then 3500. I like to be around 32/3300.