As long as we are on the Infield (one word) Fly Rule, two questions, neither about hunting.
1) What is your thought/limit for separating a fly from a line drive in the case of a blooper?
2) Do you lean toward calling IFR or not calling it if in doubt about question 1?
Please ignore location, effort, etc.; just about fly or not. Yes, the definition is any ball in flight, but for IFR purposes a line drive is not considered.