How to bi-amp using mismatched amplifiers

If two different amplifiers are incorporated to bi-amplify loudspeakers, what's the best way to match their gains? If you want to learn more, grab a copy of Paul's new book, The Audiophile's Guide. https://www.amazon.com/Audiophiles-Guide-Stereo-Paul-McGowan/dp/B08STSRW49/