Over the decades I've ridden without mirrors , with mirrors, mirrors in the stock locations, end of the grips, and under the bars, extended stems, one mirror, two mirrors, etc. Whatever worked for me at the time. To be honest, no one I know just relies on their mirrors when riding so kinda moot where you put them.

On my current Sporty I put them under the bars as they work for me better there. The short stem on the stock bars were blocked by my oh, "wide" shoulders...hah! I didn't want to put longer stem mirrors on (don't like the look) so the stockers work well being under the bars. I don't find them any harder to use or less safe mounted that way.