A couple of additional thouhts....
You are going to have to up the ISO, in order to maintain a reasonable shutter speed with some what wide open aperture.
Focusing is going to be a problem, so the by stopping down you will be able to open up the depth of field, which will just put more pressure on upping the ISO and the shutter speed.
Something like catch in focus will help, especially with a manual focus lens.
You might want to buy the cheapest lens you can find and see if any of this works, before putting in $$$$$