I have 14" apes with my mirrors mounted under. Its a pain in the butt. I half to move my arm and head to see anything. Im going to mount them up top. Its not that big of a difference. But with 16" I would try them under. And just see how it works for you.

 

Also one on left, below.

 

I'm not riding a Dyna, so I may not be welcome here, but I have 16" apes and put them on top just simply for that fact that this way allows me to always see them. I tried them underneath for a while and did not like it just for the fact that I had to really shift around to even see them. Have you thought about maybe getting a "bar end mirror?"

 

Below, and only one imo.

 

above. check out Odin mirrors on ebay.

 

I like them under the bars on ape hangers. Admittedly, I move my arm to see the whole mirror. I rarely use mirrors for anything other than to see directly behind me. I always look over my shoulder for lane changes.

A bar end mirror, especially, the wrap-over style are really nice. They are out far enough that you can put them under or over without obstruction.

These mirrors look like they would do the trick for a bar end style.

 

I have 14" flying apes and tried them delow but did not like having to move my arms so I moved them to the top.