Use AccuRIP; if there are no areas less than 100% black, you should not get any halftones. We use a T3270 too; dye based ink, the photo black epson ink. Don't try the matte for films. Yes, you can see through it, but it blocks the UV light and burns fine. In the old, old days, we could burn screens with masking films called Amberllth and Rubylith; they were transparent, but blocked the UV light, and that's all that matters. We've burned a few thousand screens with the films from this printer with a 5K Metal Halide lamp, so you should be good.
Steve