Well I went to get the 'buy 4 get 1 free' deal, then tried to add Scott's code in and it would not let me do that. I could only use one code at a time. And using Scott's code got me the best deal. But I held off due to me thinking I could get an 'additional' discount, but could not.
[edit] I sent in a email to GM to see if it is suppose to work. Will update when I get some info.
[Update] You can not use both codes at the same time. IWO, you can't get one free and use Scott's code at the same time/purchase.
But when purchasing one, two, or three pack, or one of the big bundles, use Scott's code. You will get off a good chunk.