Hi, I'm looking at erecting a small pergola, only around 2.4m square, really only to provide some shade to a small garden patch, but don't want it to look too heavy & bulky. I already have four 100 x 100 mm treated pine posts which I'll use, but want to keep the beams and rafters as light as possible. Can anyone suggest appropriate dimensions for the wood? I've seen that treated pine at 280mm x 42mm for beams and 185mm x 42mm for rafters is recommended, but I'm hoping I can safely get away with something less heavy given the relatively small size. Any suggestions would be greatly appreciated. Many thanks.