It's just how I do it - not sure why or when I started ! I just push my keyboard back where I reach it from resting most of my forearms on my arms on my desk, then wherever my hand ends up when I rotate at my elbow toward my chest is where the mouse goes. For me, it feels more natural than having to go the other way, but I have been doing this for ... ever. I mean, laptops kind of do it this way too... (I say defending myself because I know it's weird)
Insane... or brilliant?! Thanks!