Hey Brian,
Ok... all important points to understand and we absolutely rely and appreciate all your help on running the current AMPRGW solution. Before even jumping to conclusion, we'd need to know if GRE really would be more successful than IPIP. In Brian, N1URO's situation, I'm curious if a Comcast "Business" class service would remove some of these intentional filtering issues.
We, as "power users", have to pick our ISPs wisely for our specific use cases. Unfortunately, that negates us from the higher performance solutions (Cablemodem vs Wirless vs DSL).
--David KI6ZHD