>Maybe it'd be a good idea to make one hundred percent sure that they actually exist (or else that they're definitely below the limits of LIGO) before building another expensive instrument.

Hmm. I'm not too familiar with that research area. Isn't the point of detectors like LIGO is that we don't know how big they are typically?

How do we make one hundred percent sure that gravity waves exist? What do you propose as a way that would convince ourselves that they do (or don't), and how do we estimate their size? Has the research community done this already?