As far as I understand pre/post, the implementation is to put the effect only on one set of channels, the other gets a bypass. Of course, all effects are now mono – whatever that means. This allows you to plug your guitar in to input 1, ouput 1 goes to your amp, effect send goes to input 2, and output 2 goes to effect return. If this is the case, then what you describe would give you a series/parallel – but with mono effects.
What parallel effect(s) are you looking for?
