That is ass-backwards way of dealing with margins. But it worked in the past (I've tested that but can't remember if I did on Kindle 3 or PW1).
Speaking of modifying JARs: has anybody ever tested doing that on Kindle models that use Safe Boot?

A would really like go get back to having changed text sized in Aa meni also for KFX books (via CONTENT_FONT_RAMP) now on PW5 like I had on PW3... and that needs a tiny edit... But not having a safety blanket in form of booting into diagnostics makes me very reluctant to be the first one to test that