Normally, MF film is the thinnest, 35 mm is thicker and sheet film is even more thicker. MF can be found in the range of 100-110Ám, 35 mm film is around 120 Ám and sheet film 180 Ám or more.
IR 400 is made from aerial or traffic film, which is only available in on base thickness, usually around 100Ám. This is ok for MF, gives slightly problems in handling 35 mm but ist much to thin for sheet film. This is part of the price we pay for having that film in all formats. It is not specially produced for pictorial photography, and we have to live with the consequences.