Can someone tell me who to figure this out? I had a wiper motor for my windshield on the cab I'm building, but it travels way past the area of the glass on both sides. So I see they sell adjustable sweep motors, but i'd like to know how I figure out the degree of sweep I need. Windshield is 23 1/2 inches high, X 29 inches wide. Hole I made for the motor shaft sits about 2 inches above the glass. Anyone experienced at this? thanks in advance