Thread: 3.8m pergola rafter span ok?

Hi all
I am planning to build my first pergola! Its in a small courtyard and will be 4.8x4.8. I want it to be quite expressive so would like deep hardwood rafters nom 200x50 at 300cts.
The overall rafter length will be 4.8m with a span between perimeter beams of 3.8.

From my reading of span tables 200x50 will span 3.8m, however I would like some advice whether or not once the timber starts to weather is it likely the rafters will sag, warp, bow? I would prefer to avoid a mid beam and more columns as there are soakwells and sewer lines to dodge. I guess steel perimeter PFC beams connecting the four posts and a bolted mid beam are a solution but will chew a lot of the budget.

I can source 190x45 pine; 240x45 pine; 150x47 merbau; 200x47 merbau. Would any of these sizes, type of timber be preferable?

I will also have a go at hunting down some recycled hardwood roof timbers.

appreciate any practical advice.