PT10 HD system can't cope with session created in PT10 (LE)

[LizS]

Has anyone else come across this?

I have opened a session in our PT10HD2 rig that was created in someone else's PT10 rig. Most of the plugs and channels are inactive as there are not enough voices (we're at the max on the playback engine). I tried changing lots of the plugs from native to dsp which freed up some voices but not enough.
The other problem is that the mix is massively peaking and is unlistenable.

So... I changed the engine to 'aggregate i/o' and it reopened with every track and plug active (all native) and no distortion but the sound was coming out of the back of the computer and not through the 192s.

a> how can bypassing the 192s make this a far more efficient and workable session?
b> is it okay to just go native like this without any dsp plugs?
c>I've lost outputs 3 and 4 which I use to a/b with so is there a way to get the sound back through the 192s without encountering all the previous issues?

Bit complicated but can anyone offer some advice?
Many thanks.