Or you could start from "scratch" with an Ubuntu
mini.iso, change your sources.list and preferences to Mint and then add LXDE on top o that. Then you get a very light LXDE-only system that you can configure after your own taste.
It is a bit more work, but it might be worth it if the end result is an OS that is customized (and also quite mintifyed) just the way you want it. And I have to say that it seems that it was a lot less complicated than I thought it would be.
Squeezy made a post about how he did this to create his own XFCE
here, and I wrote a bit about my attempt at setting up the LXDE version
here.
I'm still working on customization of my OS (on vacations, so I don't see my computer as often as I want to) but so far I'm very happy with my setup.