What sort of trainers does your friend use? I recall Daws used K-Mart specials or something and trimmed them down with a razor to under 5 ounces.
My guess is that, if you wanted to go minimalist for whatever reason, you'd NEED to walk in the shoes for a while to get adjusted. Someone here who posted suggested wearing them for a month (?) to begin the process.
It may well be what Nobby suggested: it might feel just short of going barefoot. I'd do a mile a day for a week or ten days after the one month breakin...then maybe add a mile every other week until I could cover 10K a day in them.