Theoretically a mid will wing acheve that nirvana of neutral roll stability. Totally neutral roll stability is that characteristic most often referred to as 'that stays where you put it' tendency.

A low wing can acheve this just as well but not with a totally flat wing. For this configuration to acheve neutral stability it is neccessary to use some dihedral, not a lot but some. This dihedral effect can also be acheved by wing taper and or root to tip airfoil transgression.

A high wing cabin type can also acheve neutral roll stability but but to do this you must use anhedral. I have bashed several trainers for the heck of it in the past with dumbo ear wings (several inchs of droop) and the results have been most delightful and pattern like.

John