IMHO - no point in EQing before DAT. Worry about that later when you have a better listening environment.

I would NOT use spaced cardioids for this recording. I'd use XY or ORTF. As far as placement goes, I'd have to say use your ears.

First, with the group in place and singing, walk around and find the spot in the room where you think they sound the best. I always to this with my eyes closed. For some reason my ears go to hell when my eyes are open - I get distracted I guess. Listen for the amount of reverb, the stereo spread of the singers, etc. How far away you are will depend on the music, the room, the singers, and your personal taste - but you'll likely be fairly close to the singers (within a few meters).

It is also worth trying the choir in different locations (assuming this is a recording session and not a live concert recording). Use your ears as the first estimate for mic location.

Have some good headphones with good isolation, set the mics up - and start listening again. Starting at the location you thought was the best sounding, put the mics up and listen again - move the mics up, down, closer, farther, adjust the angle, etc - just experiment. I like to do this with a boom in my hand rather than messing with a mic stand. I can just wave the mics around and find the sweet spot.

When tweaking the mic arrangement, pay close attention to the stereo image - you want a nice, even sound stage across the front. Of your mics are angled too wide, there will be a hole in the middle - too narrow and the center will be strong.

One test I do is have a single voice walk from left to right, always facing the mics, and just sing LA LA LA as they walk across the stage. The sound should be nice and even as they pass from left, through center, to the right.

Each recording setup is different - you really need to use (and trust) your ears.

It's too bad you can't set up a few sets of mics, so your engineer can hear the differences between each. He obviously has a comfort zone, and he likes what he gets, and he's reluctant to change. I can appreciate the fact that he probably feels: If it ain't broke, don't fix it.

But as Karl's already pointed out, paying attention to the stereo image is key. I'm sure I wouldn't like the sound of a parallel pair of cardioid mics, unless it was an ususual room or setup. (Spaced omni's, perhaps, but I think you'll end up with a bit of a hole the middle with the cardioids.)

If in some perfect world someday, maybe you can setup a few different pairs, and let him hear the different arrays (you'd have to be completely isolated somewhere, with good monitoring), then pehaps he'd get motivated to do something more interesting.

As for EQ, I'd leave it alone (except for perhaps some low-end rolloff for rumble, air handlers, etc.) until it's time to mix/edit/master it. I realize you don't have many options with just a DAT, but again, leave it as-is until you're working on the completed CD. No point in adding more changes (subjective ones, most likely) at the recording stage. You have enough to do with mic placement, level adjustments, rolling tape, etc.

EQ at the recording is just one more change you may not be happy with later, IMHO.

Excellent post Karl. This is the approach to take. Definitely go with ORTF, as its a bit dry, you will probably use some reverb in mastering, so err on the side of a little bit "closer" for the mic positions rather than gamble with "too far away".