I did a major rehaul of fem_update and basically rewrote the entire primary do loop over all the rotated models. I think it is much better now because it will only call intensity once per pixel (due to the array update_pix) and it also now properly updates the model without having to rebuild it. However, it doesn't update the hutches - it just destroys them and rebuilds them. I need to fix that still. Also, check the upper bound on the do loop on line 901. I'm not sure that is correct, but it seems to me like it should be. It's just not what Paul had before (I don't know why that didn't error). I also added a remove_element function to model_v2.f90 which is similar but not exactly the opposite of add_index. Right now the algorithm runs. Whether it is correct or not I haven't checked. There is debug output in the commit as well.