It's difficult to answer this question if you're taping stealth and haven't specified the method. I'll assume you're using the classic 'beatnik hat' method in which there is some additional space for the windscreen. If you're using another method, you'll have to use your judgement. Also, you're subject line says MK4, but the content of your post says MK2. Clarification would help.
First, the hat itself will block 'some' wind. It won't help at all with a moderately stiff breeze, but on a calm day outdoors you're probably OK, maybe even better off, not running screens at all.
The B5D probably can't be used at all. These windscreens have a plastic cage inside of them and are bulky, thus they would never fit comfortably inside a hat. For Schoeps screens, I would recommend the B1 or the B5. The B1 isn't really meant to be a windscreen, it's more a dust guard, but it would help with very light breeze. It's like a slip-cover for the capsules and is very small. The B5s are more robust, but still small enough to fit inside a hat. The windtech screens are not my favorite because they're bulky, but they're cheap and certainly effective.