I tried the exact same experiment you are thinking about with my Ping i5's.....Had regular flex stock Ping graphite shafts, but noticed that I was losing distance the last year or so. So, I soft-stepped by two clubs.....5 iron shaft in the 7 iron, etc. I didn't change the lengths....just choked down. I did notice higher trajectory which defeated the purpose of my experiment (more distance!). So I pulled all the shafts and re-installed them the right way. I plan to offer them for sale here pretty soon.