I sawed & built a 66m2 deck out of green Rough sawn SBG a 6 months ago, I pencil rounded the he top corners, laid them tight & only put one nail in each board, the nail was at 1/3 distance in from the edge, the owner is going to put the final fixing nail in when he gets around to it, we had a long hot dry summer & within 6 weeks they had shrunk fully in position, it looks rustic with the gaps not exactly even but that's what the owner wanted & is really happy with the end result.
Somebody else saw the deck & now wants the same thing.
Inter