There's a forum here that deals with DIY mods. As for DIY joose the hardest part is finding the right recipe. I've got 200+ and some of them have upwards of 10 diff flavorings in them.
I guess I'm really going to have to go with DIY. Start with some simple recipes and then go more indepth. My biggest problem might be knowing when to stop. Who really needs 5 liters of various juices on hand.