Been using a Pro Chrono for archery and almost put it up for sale but going to get into muzzle loader and think it may be handy for that. I've had problems indoors but used one of the cheap light mods using utility lights and got it to work. Have you guys checked accuracy against something else? When I select sight tapes for my bow seems like I always end up with one that's about 10 fps faster.
Read some of the instructions, for arrows, you have to be more than the length of the arrow away from the first appeture to ensure the arrow has cleared the string before it breaks the first gate. Otherwise you will get wildly varying results on the slow side!