Cornwallis gets very busy even when the weather is not so good. You can still fish it when there's an easterly you just feel a bit weathered at the end of the day and you need to watch your kit doesn't get blown in the water.
When the tides running, a 4oz breakout sinker is a good option however even this will not hold its location and will get dragged. The best fishing seems to be when the current is not in full flow.
The fishing isn't usually that hot there but fish do get caught. The most common catch is kahawai, you can also get trevs and there should still be some gurnard around at this time of year. When it warms up you usually get plagued by baby snaps, chances of a keeper size snap are usually pretty slim. Through the summer there are usually a few kings hanging around too which can be an awesome sight when they're sitting in the current under the wharf.
It's possible to walk round the rocks to the right hand side and get right out to the point from about 1.5-2 hours after high with a bit of climbing over some boulders. The walk takes about 25-30 minutes, you'd want to watch out for seals chilling on the rocks at this time of year, they cant get a bit agro when you almost step on them when you climb over a boulder, but usually bugger ff out of your way. Just don't block their path to the sea.
I haven't fished there for a few years so don't know what it's like these days. Don't let the wind put you off, just take some warm clothing and waterproofs