A common issue we get reported on "certain" mics, is complaints that the Classic-Sofite isn't removing all of the wind-noise - even with all the slots (ports) covered. This can be caused by a couple of things, and is the reason why slip-on windshields don't offer quite as much protection as basket windshields.
In most cases, the issue is with the mic switches or the seal around the XLR connector. If you blow gently across them, you'll probably be able to hear the tell tell low rumble of wind noise.
The solution is very simple, a small piece of electrical tape stretched over the switches or around the XLR joint and the seal will prevent the wind getting in.