In Iron Man Mode I NEVER play less than a full party and also never play speed or peasant games when I play irom man. Playing solo in true iron man is a real job and, if not impossible, certainly improbable. In true iron man, mephistoing/agressive save-reloading is prohibited so if you don't get someting valuable from a high level monster kill or a shop on first entry, well that's too bad.I have lost parties in Colony Zod and even on the Lincoln in MM7 and have had to start over. In MM6 I have lost track of the times I have lost parties in the Hive and started over. The same with the end-game fights in both MM8 and 9 and I have lost many parties in the Plane-between-Planes and the T1000T respectively in those games also.
I don't play iron man much any more since my eyesight and hand-eye coordination has deteriorated with age but I have, in the past, completed MM6,7,8,and 9 (also the mods for MM6 and 7) in the iron man mode at least once each.