Handlebars and seating position is such a personal choice...
I'm long in the torso and prefer a fairly up right seating position...
The stock bar 4" rise suits me fairly well... Though I didn't care for the looks...
I'm long in the torso, short in the arms , so the stock bars works well for me too, but as said above, the looks is not optimal with the sharp bends.
Tried LSL sport touring bars, those were to narrow and far forward for me.
Also rode a BSA A65 Lightning with M-bars, fit me fine but thats a compact bike, and I think they won't fit me as good on the Bonnie. Guess the only way to find out would be to try. I'd also like to try those flat track bars.
My solution? Z Bars! A full 13 letters down the alphabet from M Bars!
If you like the feel of the stock bars then the UK Low bars from NH end up in a very similar position, but look "right".