In reply to Mike00010:
Whatever you do, I'd recommend having at least 600mm (preferably 1m) free beyond the width of the board itself for flagging and general movement. 5m is too high for a bouldering wall IMO. 4m max and noting wrong with 3m. I built one (not free-stand though) which is 3m wide, just over 3m high and is about 17°. Bear in mind having a decent a decent t-nut grid. You probably want each row of t-nuts off-set at about 150mm centres (in a diamond pattern)
Also, the steeper the better. I'd have done 40° if I could, but was restricted in the amount of floor space it was taking up.