That's been long enough ago that I don't recall the dimensions,and it's still tucked away in hibernation right now. Believe the side strakes were 6" on the bottom side. I wasn't so much worried about the angle,as I was the width of the planning surface and the height it rode in the water. Right or wrong I thought it would best "trap" the water and pop it up on plane the fastest by keeping the outer points close to even with the bottom of the tube. It would create a wide planing surface,and ride high on plane.
I've seen some with the strakes higher up the tube. But, it seems to me the water rolling up from the bottom of the tube will slide off the side of the strake easier,rather than having to slide back to exit the strakes. Something else I was looking at when I chose the style of strake was the sharp edge. With a round edge water will drag around the strake easier due to surface tension,causing more drag. As to where the sharp edge will cut and release. The way I see it the water and air I can trap along the planning surface is more "slick" than the tube surface itself. With rounded strakes mounted higher it would seem that a lot more water has to drag across the aluminum as it's being drug off the side verses trapped and directed back.
I don't know if I'm explaining this right,or if that made any sense. I suppose this could be debated all night. I do know it'll pop up in about a boat length, rides really high on plane, and stays on plane down to about 13-14 mph. I run pretty heavy when I fish with all the gear,people,and water in the tanks. So I've been happy with it's performance.