Even though I wanted a nice place to put my ballasts, I didn't want to do the flapper mod. I once owned a brand new Mazda3 that I mutilated with strange electronic mods (laser sighted airsoft gun, IR cameras front and rear, police scanner, PA/CB radio, lighting, etc...). Having bought my 1krr new as well, this time I am leaving as much of it stock as possible.
Anyway, I ended up putting mine on the little tray beneath the headlights. The slim ballasts fit perfectly and the wire coils nicely out of view. The only thing I don't like is potential exposure to water, but the fender should mitigate that risk. DDM has a good warranty anyway, I have exchanged a water damaged ballast (from a car) before with no questions asked.
That said, I don't know if the '08 has the same little tray that the '12 does. So, apologies if I have wasted your time, but maybe someone else will find this useful. And in my application I am going to run a cutoff switch, so I haven't hidden the wires entirely yet.