Viper Archery
I am not a fan of Viper Archery at all.
While I am not farmiliar with thier line of sights, they have been pretty unreliable with regard to some of their other products, namely their D-loop pliers.
I ordered a set this past February during the Harrisburg sportsmans show. Delivery was supposed to be 3 weeks. Here we are in the middle of November and they are still giving lip service about delivery dates. I have been getting the "3-4 more weeks" line for nearly a full year.
Some of the online verndors have received their shipments, however those of us that supported Viper when they were trying to get their product off the ground are still waiting.
IMHO, you can find much more reputable and customer service friendly companies to deal with.