I did mine almost exactly like you described. And went back over it twice. Loosened the frame mounting bolts slightly, Front bolt tightenedMy 2017 Wee doesn’t buzz with the Givi bars. Maybe loosen all bolts and while making sure the front (cross) connection is well aligned and has the o-ring in place tighten everything again evenly and do the front last. To remove any potential tension or loose play.
My 2018 1000 has started doing it now around 24k, was perfect before that. I'm going to try a few of the tricks mentioned here.Update: spoke extensively with Givi USA about this and they are absolutely unwilling to help. Buyer beware.