looks about the same size as my back yard... i finally had to stop playing in the back yard because me and my friends are good enough now to shoot each other off the break. back yard stuff is good for practicing and learning what you should and shouldnt do when playing but it never beats a real field.
definitely DO NOT use 300 fps speed on a field that small, we use 240 fps or lower in my backyard that way even in close quarters (all the way across the field
) no one gets hurt. if you cant tell, stand about 50-60 feet away from something like a fence or large bunker. if you aim for the center of it and it the paintball hits the bottom 1/4th of it or lower you probablly have a good speed, either that or really bad aim
another way to tell without aiming is if you hear about a 3/4th second gap between when you shoot and when a paintball hits something 50-60 feet away