Using various precision measuring devices, I see that a 55 negative is 0.0051", and TMY is also 0.0051", (post processing) but my Pan X is 0.0070" - 0.0074". (pre-processing).
TMY measurements taken from 120 and 35mm. I need to confirm it on 4X5. If so, that will make it easy to at least hit the thickness as 55 using TMY. Later...nope 0.007" on the 4X5. Kodak claims that the 4X5 is on what they refer to as the Estar base (polyster) but that the 35mm and 120 versions are on acetate. This does not seem right to me - I am looking at some right now and have my Bic lighter ready to go.
Hunting around for some TMX here at the lab - I have plenty at home so I may have to wait until tonight.