Tryin to build an indoor gym including an A frame swing set thing to hold a banana bag and a teardrop bag. Legs are 4x4’s and cross beam is a 4x6. I need the top of the cross beam to be approx 9ft (108 inches) to get maximum lift and not hit my ceiling. How long should my 4x4’s be to achieve this. Picrel is the brace will use at both ends of the frame. The 4x4 will butt up to the the 4x6 as shown by red line in picrel.