My Bav 30 had an aftermarket windlass installed when I bought it, in a similar configuration to what you are looking for. As with all bavs, if you don't opt for factory fit windlass, they cut the shelf back leaving you with a bit of work to do. Main advantage of a vertical windlass mounted on the remaining bit of shelf is it leaves room to actually put the anchor in the locker - handy if picking up a mooring buoy. My install was poor - only 2 bolts actually bearing the weight. Also, the run from bow roller to capstan was around 15 degrees meaning the chain didn't enter the capstan straight so the chain could jump off. I reinstalled the windlass by having a box made up that lifted the windlass up and also inclined it to get a straight run on. This was all a bit of a hassle to fabricate in mild steel then galvanise. If I was starting from scratch, I'd probably install a horizontal windlass, but I had a vertical, including a hole cut down through the back of the shelf and into the front cabin, so I was a case of making the best of it. Attached photos should help. PM me if you want more info. Windlass is South Pacific and designed to be mounted proud on deck, not on a shelf under the locker lid.