RE: Thurman scopes
I have an HHA optimizer lite site and I bought the Pro 19 head with a 4x lens from my HHA dealer for it and it works well. If I remember right you got the HHA right? That may be an option.
As far as the Thurmans, I have heard both good and bad about them. I know alot of guys shooting Bullseyes and they all seem to love them.