I pushed it to 400 - Caffenol C-L, 80min stand @20C, agitate first minute and two turns at 40min - and it did remarkably well. Grain was not an issue, and it maintained pretty good tonal separation. Frankly I think it handled a two stop push better than HP5+, at least in my limited experience in doing so. I certainly wouldn't hesitate to try it, but I'd definitely use a compensating developer.