the dps is split odd parts to dsp1 and even to dsp2 so best sticking to your 1-6. however that said you need to try and spread out the intensity of each patch, use the battery indicator to do this, ie dont have all patches with full bars on all odd parts etc.
As for outputing parts over 6 mono channels, no probs
hope this helps,
I'd also advise you don't use the "chord" option on arps as there seems to be a problem with stuck notes
see rom 100
cheers
Kris