Correct, from the initial posting I did not know it was for heavy pedestrian use. We are mainly an exporting company but sometimes arquitects or contractors contact us directly with almost impossible orders. We just sell a few widths (90/95/120/140 and 145mm wide x 19/20/21mm thich and random lengths) while these arquitects or contractors require specific quantity of boards of a certain width and even specified lengths!
Orders like this will reduce output (#boards produced per log) will reduce significantly and sometimes this doubles the price. It is true howver that the quantity of substructure will be reduced, however, substructure is a fraction of the total price so this is not quite the argument that would justify the request for 35mm thick. Also labour is more affected by the lengths of the boards (more boards to install per m2) then by the thick of the boards. Anyhow, heavy pedestrian use would justify, or just a client with a big wallet who doesn’t care.
So if you need good quality for ordinary use, just order random lengths, standard thick and in respect of wrapping and cupping do consider narrower widths! cheaper and safer.