You don't have to stay out of IFPA tournaments. Try looking up the ranking of Bowen Kerins... Or Chris Newsome.
The problem isn't at the top - it's in the vast majority. You are asking for precision from a system that doesn't have it across the baord. The narrower the bands are... the more precision you are asking of of the system.
It's fine to look at your foot.. and estimate the size of a room assuming your foot ~12". It's entirely different to build something expensive or uncorrectable using your foot as your guide.
Look at top B qualifiers.. the top 4 were ranked 205, 2129, 165, 542.
Top C qualifiers...447, 817, 831, (?)
It's not unfair to say that outside say the top 250 or so... the quality of an IFPA ranking quality really starts to slide.. and not too much further goes to junk when it comes to comparative measurements.