1) You will probably lose about 60fps with those 2 inches of barrel. Trajectory should be almost the same, but always round down. 2) A rock solid rest is THE most important part of sighting in. If you are moving even a slight amount, you could easily double the width of your groups, have many "fliers" etc... 3)Manufacturer trajectory tables can be reasonably trusted, but always practice and check. Most popular is a 100 yard sight-in, up to 3" high.