Would it be possible to replace one of the film polarizers (on the LCD) with a circular polarizer further in the chain (ie: at the triplet)? I'm not sure if this is an obvious optics issue so if it is please correct me.

Short answer. No.
Long answer. You need a linear polarizer. You can put it wherever you want in the light path (with variable results).

See: http://en.wikipedia.org/wiki/Polarization

EDIT:
You might have mixed up the terminology.
If you're talking about a linear polarizer cut in the shape of a circle, then yes, it would work (you have to rotate it to match the degree of the other polarizer + 90).

Hey there.. actually I was referring to a camera circular polarizer (spins freely to accommodate changes in light on the fly - think we're talking about the same thing in different versions ). And yeah, did work. Stripping the AG off revealed that the sheet was a combo AG/polarizer.. nuts. Attaching the polarizer to the projection lens and spinning to accommodate the remaining polarizer (still on the opposite side of the LCD) produced what it was supposed to!

Just a quick, instant & cheap ($15 @ Bestbuy) fix if anyone else makes the same blunder. I'm using the standard 15 set (purchased a couple years ago - finally putting it to use) and the matching filter is 67mm - you'll need to make your own mounting to attach the two (tape works fine).

So you are using a camera glass polarizer at the back of the triplet? How does this compare to the quality if the polarizer was on the lcd itself? How did you mount it?

Member pbassjams last visited the LL forums on 20th July 2008.
If you PM them, you might get a response if they have their PM set to e-mail them when a PM is received.

You might be able to find something of an answer in this thread.
You can also try this Google search: site:lumenlab.com circular polarizer
Or: site:lumenlab.com camera polarizer