If the double beam is tied together, one at 1600mm on one side, and one at 3200mm on the other side. If spaced, one in between at 1600mm and one at 3200mm., I would say. Mr. HandyAndy - Really
hello girls Using a double beam with 2x 6"x2" with 4x4 posts are usually every 1800 centers, I believe! happy to be corrected if I'm wrong
So we're talking either 4 or 5 posts either evenly or unevenly staggered. I would go with 4 or 5 evenly spaced posts.
It's better to install the two outer posts first, then run a string line, this will ensure all the posts are straight.