You have a couple of options. You can get a lip like an ITR lip or WW RS, etc. You can also get a splitter, like those used on Realtime ITR's, where its basically a low ass spoiler connected by chain to the bumper in the middle.
You can also get fins like those on the RX7 made by ARC or JIC maybe? I dont remember for sure. I know Ings+1 makes fins for the DC5, but doesnt CWest also make the fins for DC2?