Hi,
The 3/16 should work , check if you can with tower if yuou can. 4.1 divded by 25.4 = .161 of a inch and thats just .025 thousands of a inch under 3/16 and you need a little clearence.

Had a thought, when I order something like this , I would order a few more and or different sizes. With cost of shipping ,etc more than likely you will need more of that one or some of the next two sizes around what you want. Just my thought, I general have what I need and don't have to run to town or specal order anything. But I have been a packrat for some years!!!!!!!!