Yeah its not exactly clear, any ticker in basic, but its delayed unless you pay
for a subscription to the relevant exchange - $6.50 for Eurex.
http://www.ninjatrader.com/support/forum/showthread.php?t=53646
Don't think they do cash markets.
Things like EURUSD and 6E are pretty much identical.
I don't know about DAX and FDAX though, I do know there can be a fair bit
of variance between DOW cash and YM so its worth looking into that variance for sure.
Depends how loosely you are willing to interpret FDAX volume as a proxy for cash.
TBH though, what you are doing looks to be working well, so I'd be wary of
fixing what ain't broke, but thats just me.