I learned a scary lesson on ankle carry years ago.I was blindsided by a big guy and we went to the ground.I ended up on the bottom and at that moment the lightbulb came on.
In my position I was unable to access the J frame on my ankle,but guess who could? All he would have had to do was turn his head and look back to see it,then reach back with his right hand and draw it.
It's what I refer to as an epiphany. I got him off me and came out better than he did.I got lucky. He happened to be an individual that I had arrested before and, though he was drunk,he recognized me.
I will not use ankle carry to this day. I won't hammer anyone who does,but I feel that it has more disadvantages than advantages,and is a dangerous practice.
I was off duty at the time and the J was all i was carrying.
I prefer to have a backup these days,and one that is accessible with either hand. Just my experience and opinion.
YMMV.