Ok so, I'm heading into the studio tomorrow to do an assignment for my audio tech class.

The assignment is to record 2 acoustic instruments (one chordal - guitar, piano etc and vocals.)

The catch is we are to use no effects, no eq, no compression, no nothing. Its all trying to teach us that you can't polish a turd.

Anyway, so I thought i'd try something different and use a pzm mic on the guitar. My plan was to slap it on the soundboard to see what kind of sounds i could get.

So what i wanna know, does anyone have any experience or other ideas for the placement of this mic?

I wouldn't put it on the soundboard myself, that would be crazy loud and hugely bassy and generally just messy.

I once recorded an acoustic guitar with two pzm's on a pane of glass about half a metre away from the guitar in a spaced stereo pair with baffles at either and of the guitar. Perhaps something along those lines?

Basically if you have a nice painted wall or reflective surface, putting a pzm on it and facing the instrument towards the surface will give you a fantastic, bright, crisp sound.

P.S. For the record, the pane of glass technique also works wonders as an option for drum overheads.
You may not want to put it on the guitar itself. Too much proximity effect, AKA boominess, or overdrive the mic. Whatever they are attached to will turn that surface into the mic. Possibly try on a flat wall or in a corner. Face the guitar in that direction and play around with the distances to find a desired sound. The reflections off that surface could create a natural delay and add some air for ambiance and depth.
I once taped a PZM to the guitarists chest just to hear what it would sound like from his perspective.
All my guitars are old enough to buy beer, are You?
I did end up going with the mic on the soundboard, no real issues with proximity effect. There was definitely a lack of clarity, but teamed up with a couple of x/y crossed neumann km184's 6 inches away from the 12th fret and a AKG C414 a couple of metres away pickin up ambience - it sounds huge. and crystal clear.