two Sparkfun MP3 shields at once?

I'm in the middle of a project that needs two MP3 shields running off the same 'duino

My plan is to create a super-shield
the first MP3 player sits in the normal place
the second sits beside it
I plan to use different pins for the SD CS signal and the 4 MP3 control signals

is this a feasible approach?
anyone done similar?

advice most appreciated
TIA