I have the Silhouette as well and just put on a 40mm obj scope; I looked at all the alternatives (Millett, Leupold, CZ, Talley) and ended up using the 11mm High Rings from Leupold. I was hoping to find some CZ rings as they are the cats-meow, so I'm told, but they weren't available anywhere in Canada and the Leupold rings ended fitting really well.
I would certainly recommend them - I got mine from Prophet River in Edmonton, Clay was super great to deal with... Shipped the day I ordered and they got here, NS, 2 or 3 days later. I was very impressed.