Whoa, that is some serious zoom... Looks good, but I have a feeling it will be almost impossible to position it so it picks up the hits, unless the target is 75 to 100 feet away.
Paintballs curve as they fly, and that drop affects where in the picture frame the person will be depending on how far away they are. I don't know how your 50mm lens compares to my 5X zoom, but just looking at that, I would guess that is like 25X zoom... Which would work with a real gun, but you are lobbing paint? So the drop will put them out of the tiny frame you can pick up.
Course, you are using first strikes, I have Zero experience with those, do they fly flat long range like that? I would assume they still drop, but not as much as a regular paintball.
Maybe you could set up a pivot system, where you could "dial in" the distance of your shot before you fire, and set the camera for that range, then pull the trigger. You could dial it in by locking your marker to a table, and figuring out what range and angle you need for each distance.
I've seen a guy at CPX that uses the same set up you are (except with contours) and he has two of them on his barrel at two different zoom focal lengths, it looks pretty good! But, he is rarely shooting more than 75 feet away.
I want something that does up to 350 feet away, and everything between. So I don't have to touch it while playing.
Just remember to always test it out before you play, so you know it is lined up right. Nothing worse than playing a whole day only to find it was tilted to the left or right, and you have NOTHING on film... Been there, done that...