How do you rotate injection sites?

I've been following the link below, moving regions every week; and an inch away from the last injection site.
http://www.diabetesforecast.org/2016/sep-oct/injection-site-rotation.html
I have used the back of my legs and calves and buttocks too, which aren't on the diagram.

 

I move areas every week. Keep buttocks just for basal and swap buttocks each week. Abdomen, stomach, left and right thigh. So basically a 4 week rotation. Occasionally upper arm. The difficulty is absorption and reaction speed. So on leg weeks I have to remember to inject a longer time before I eat.

 

I use legs and stomach for fast acting and top buttocks for long acting. I am a bit haphazard with remembering my last site though, and aim for somewhere different or the other side, but I should try and come up with a clearer system. As it’s at least 5 times a day usually.

 

I always forget to move. I tend to find it a little sore on the stomach so Iv just used the top of my leg for ages now. Iv never had any issues with dose so never felt the need to change
If I'm sat in a bar or restaurant I'd just jab it in my stomach

 

I use the grid from the diabetes app 'Diabetes:M'. But can't reach all of them so just follow what I can.
A web search will reveal many area/grid systems for you to choose from.

 

breakfast left thigh, dinner right thigh, tea alternate sides of stomach and basal alternate bum cheeks xx

 

Is there a reason why many people don’t use the top of their arm nearer the shoulder? Was thinking about trying to alternate it there but don’t see many others using it?