There are a lot of 'tops' in your original post. I'm not sure what you mean by this:
My pump will be below my mash tun (Ok)
and then pump up into the bottom of my rims tube with the element on the top (are you saying the tube is oriented in a vertical position with the element connections on the bottom and the element pointed up towards the top of the tube? I think a picture here would be worth a thousand words)
and then flow out of the top of the rims tube (If I get this right, you're pumping into a vertical tube where the element connections are on the bottom, with an inlet in the middle of the tube, and the outlet at the top of the tube.)
back to the top of the grain bed. (Ok)
I can't speak for most people, but my tube is horizontal with the wort coming in on the left hand side where the element is screwed in. The wort then runs the length of the pipe, heating is it moves along it. At the outlet tee I have a temperature probe to read the wort temp. If the objective is to not overshoot the temperature then that's where I'll read it. Just before it exits the tube.
Temp probe on the far right.