I found a lovely roll of Ilford HP4 (135) with expiry date "March 1971" in its original packaging. I got good results with overexposing expired film one stop per decade since the expiration date. So I'd have to overexpose the HP4 ~4 stops. It's rated at ISO 400. Since I don't want to go lower than ISO 100, I'm thinking about exposing it at ISO 100 and push it another two stops during development. Which leads me to the question: how would you develop this film in Rodinal? I tend towards simply developing it with the same times as HP5+ with a 1+25 Rodinal solution at 20°C. The other alternative would be stand development the film (which I've never tried). I've seen remarks on this forum that stand developing this particular film works as well. I'd appreciate any advice. Cheers!