Hey Wingers,
I've seen offshore wind wingers going for it along the Perth coast in a straight Easterly. I've personally foiled with wing in South Easterly winds from Whitfords which is 45 degree offshore changing to directly offshore once you round the point at Pinnaroo.
Off shore winds are rideable, but seldom pleasant. Always gusty and filled with holes. Sometimes it blows for 15 minutes only to stop for 10 minutes and then return etc. Riding in these conditions is only really practical with a nice floaty board that you can sit on and wait in between the gusts. No wing size will be perfectly correct but I would rig for the average speeds or gusts, not the lulls.
It's very difficult to ascertain the wind strength in offshore conditions without an anemometer. I've been worshipping with for more than 45 years and still struggle to estimate offshore wind speeds. Take into consideration that the disturbance of the wind exists for 7 times the height of the obstruction. This is the case in steady winds, so when you add in the turbulent nature of offshore winds, the disturbance can be amplified and the wind may not stabilize for more than double the 7X rule.
When venturing out in offshore winds, pick a distance to keep within. Ideally this should be a distance you can easily paddle back in, taking into consideration that you may end up paddling back into a blustery headwind. I'd suggest 400m as this is the legal limit before encountering maritime regulation. If you reach your distance limit, lay on your board, tie the wrist strap around your foot and drag the wing in (assuming you will continue wing foiling), otherwise, deflate the wing and roll it up, lay down and paddle in.
A good idea to tell someone where you are going and when you should be back. You can VERY quickly end up too far out, end up dehydrated, suffer a cramp and not be able to paddle against the wind. Or find a mate to wing with to accompany you.
DM