What do you mean by high speed? If you're talking about being up on plane, you will probably have issues regardless of the location, because there's nowhere you're not going to run into some sweep-down of bubbles. However, moving it toward the center-line of the boat will give you the best chance to get it in laminar (no bubbles) flow at any speed. Don't mount it directly on the center-line or aft of anything that is going to disturb the flow of water, like strakes or through-hull fittings. You're pointing to just about the right location in my opinion (though I can't see the bottom of your boat forward of that), a few inches to either side of the keel.