If I can make one suggestion?
8x24 = 192 Sq ft. Perimeter is 64 linear foot.
16x16 = 256 sq ft. Perimeter is the same 64 linear foot.
If you mount a 4x4 in the middle of your 16x16 area, you not only have roof support, but using two 8' wide panels, you can now reconfigre the space in multiple ways. AND about 25% more space.
8x24 = 192 Sq ft. Perimeter is 64 linear foot.
16x16 = 256 sq ft. Perimeter is the same 64 linear foot.
If you mount a 4x4 in the middle of your 16x16 area, you not only have roof support, but using two 8' wide panels, you can now reconfigre the space in multiple ways. AND about 25% more space.