User blog comment:Guts!/Anime Depiction of Luffy's Gear Second/@comment-972068-20130528014001/@comment-5640399-20130528210248

Guys, why would Luffy want to use G2 in only one limb in the first place? G2 damaged his body and shortened his life and while Luffy didn't really care about the shortenig life he wouldn't want to be hurting himself when he uses one of his greatest weapons. So by isolating the change he could keep the damage away from his organs minimising the repercussions, but in a really tough battle he's gonna want to use in in his legs for speed, his arms for most attacks and eventually he will just be using it over his entire body! Also, on the cover of Vol 65 all the steam originates from the Red Hawk.