Been doing internegatives on tungsten film for a while now. It works extremely well. You do need to overexpose and then underdevelop to tame contrast, and sometimes add a bit Y filtration for some very cold Velvia shots, but generally the biggest worry is dust. I'm using grounded metal Hama contact printing frame, anti-static wipes and a dichroic 200W-bulb enlarger. Get a good supply of same-type and preferably also same-batch tungsten film, test it thorougly and you're in business. Mine is Kodak 100T.