Answer = yes. Christopher Wong and Daniel Waldorf at Cal Poly did some extensive testing of different methods and found ordinary transparency film to be quite adequate.
Thats going to save me several hundred dollars over paying for several stainless stencils.
http://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1054&context=ime_facThey conclude in their paper:
After completion of this project, it can be concluded that:
1. Plastic copier transparency film is a successful alternative material for stencil manufacture.
2. Solder paste technology has advanced greatly and its use on plastic has no adverse effects.
3. The application of a laser cut plastic solder paste stencil is a resourceful process that may used in electronic
manufacturing, particularly for rapid prototyping of SMT boards or short run production.
Recommendations for the implementation and use of a plastic solder paste: stencil include:
1. Verify the proper aperture ratio for printability of solder paste through stencil.
2. The orientation of the stencil should be aligned with the squeegee print direction stroking along the axis of the
majority of longer pad dimensions and perpendicular to smaller pad widths.
3. To print results, similar to a metal stencil, use a light pressure and slow speed squeegee stroke leaving a thin
film of paste over the stencil. Angling the squeegee towards the print direction may also aid in print quality and paste roll.
4. Peel away plastic solder paste stencil rather than lifting straight off to prevent scooping and shifting of printed paste.
5. If printing repetitiously, or for more than one stroke through the stencil, be sure the underside of the stencil is
clean fiom solder paste, otherwise bleeding may result.