There is probably more than one way to do it johnvox, but since I did it myself earlier today, I will give you my method.
If you haven't already got it go to http://ubuntu-tweak.com/
and install Ubuntu Tweak. I am not using LMDE myself but I have done in the past and if my (unreliable) memory is correct it should run well enough. When you have installed U-T you go to the 'Tweaks' section and click on the 'Workspace' icon. You then set the horizontal and vertical sliders to 2 and that is it done.
Fujitsu Lifebook AH532 Laptop. Intel i5 processor, 6Gb ram, Intel HD3000 graphics, Intel Audio/wifi. Realtek RTL8111/8168B Ethernet.Ubuntu12.10 (Unity), Mint14 (Cinnamon), Manjaro (Xfce).