Here's my results. i was not able to attract many customers with my mason jar (actually a plastic jug) trap. I tried 3 different types of bait. Lunch meat, peanut butter, and tuna. I only caught 3 or 4 flies in 2 days. I used 1/4" holes like you said radar.
I got so fed up I wnet and bought some Raid Flying Insect Killer Formula 6. I will probably die of cancer in a year but I have NO FLIES! That stuff works immediately. I have 1 or 2 show up over the period of a day but I quickly swat them. All I did was soak the sides of my garbage can with the spray and also the entire shop floor. I don't plan of licking my shoes any time soon.
The flies are virtually gone. I know these carcinogenic sprays are not a good idea but I do not plan to use them often. i don't think I need to. There are dead flies all over my shop. I watched them land on the side of the can and in a few seconds they would fly off, do funky spins in the air, drop to the floor, and go into convulsions before going off to fly heaven.
Like I say, I may be clueless but I am also nearly flyless.
