Hi Sacguy71,
Well the concept of Doepfer cases is a bit different, that's why you can't lay them down. You can lay it down but you might not like the power plug make it "wobbly" ;-)
The idea instead is to use A-100LMB base case first (that gives you a half-laying/half-standing case) and on top of that you add a standing monster case.
I don't have an MDLR case, I was considering one however the power supply specifications aren't as good as those of Doepfer and the MDLR cases are more expensive on a per HP base than the Doepfer monster cases. I am actually (very) happy with the Doepfer (monster) cases, they provide some nice affordable space and are deep enough for most of the modules in the market.
Kind regards, Garfield.
For review reports of Eurorack modules, please refer to https://garfieldmodular.net/ for PDF formatted downloads