Our pergola span is 18' OC x 14' OC using 6x6 posts, two 4x12x20 support beams, and 4x6x18 rafters. We also added a knee joint using a 4x4 (2' down and across). The wood is cedar. My question is - should the knee braces go out further than 2' and/or should we have used a 4x6? We just finished it this weekend but it would be easy to replace. We're also considering adding 2x4x10 (or 12) boards to the top (effectively spanning 20-24' parallel to the support beams). Just want to make sure we have enough support. Thanks!