I wouldn't mind tearing one of those apart just to see what ballast they are using... As a *general rule* (not one I subscribe to for all applications) mixing ballast type and bulb types is not always a good idea... Magnetic ballasts for mercury vapor lamps use a different capacitor than those for Metal Halide application, usually causing the bulb to burn brighter, but *may* introduce life expectancy issues of the bulb... with a notable exception, the Iwasaki 6500K halides are designed for use on MV or MH ballasts, but the MV is recommended. They really shine (pun intended).

There are some that have great success using MV lamps, but as mentioned previously they are they are generally the exception to the norm, thier sucess could likely be attributed to many other factors as well as the lamps they use.

Experimentation in itself is always fun... just be kind and share in any results or when the smoke falls out.