You could always mix up a batch of C22 from scratch using an alternative formula and process yourself. As PE mentioned, E4 doesn't like high temperatures. I have had reticulation problems with it even at 85F with a pre-hardener and neutralizer. Generally E4 is lousy film, in my opinion, or at least one that takes a lot more attention to processing than the current E6 and C41 films. I am interested in how you come out with your tests because I too have some E4/HS-IR in the freezer. By now it has likely lost its sensitivity, but someday a few experiments could be fun.