Quick derailer question
 

Ok, so my lower and higher limits are ok. But the middle chainring rubs the inside of the derailer housing when on the middle ring in front and largest sprocket in back. Why is this? Shimano 105.

First, high and low stops are adjusted to keep your chain from going passed the highest or lowest chainring/wheel. They have little to do with any adjustment in between or chain line settings.

Mid front and large Rear rub sounds more like a FD adjustment issue or its just the nature of the beast.
Some designs rub in this condition, some don't. You could adjust the FD so that you get less/no rub in this condition but then it may rub in the mid-front, small-rear combo. If its prone to rubbing, adjust it for the least rubbing on each end.

The fact is, there is probably a small Front-??? rear combo that is near the same gearing as the mid front-large-rear combo. So if you're going to be spending any length of time/distance "needing" this gearing ... plan to shift to the small front - ???? rear and not worry about the rubbing.