We have an Amp Air mid way up the mizzen. It is silent but produces so little. I also have a fourwinds that i want to install. I had chris parkers old choey lee and that had a fourwinds on top the mizzen. The fourwinds really produces and has a brake that is used in high wind that is automatic (is is mechanical not electric) and the brake can be used manually as well with a long line attached to it and run down the length of the mast.
that said we are planning to do an Arch with davits to pull up a portaboat at anchor, but i'm half way wondering if davits are worth it.
