I use the one from their website. I've never seen a coupon for it. The kit comes with an 80lb adaptor even though the manual says to use a 70lb. Members here mentioned to me that dta has standardized the 80lb so you'll be fine with that.
You can message spuhr, they will recommend the best one mount for it. I emailed them and got a reply in less than a day. Just tell them what rifle and scope and they will help you out.
Mount finally came in, here she is with the new glass on there. Now I need to go out and zero it in. Anyone have advice how to properly zero in the s&b 3-20 ultrashorts? Thanks guys and gals!