well i am also a chub chub. i just got my fat boy spring in my 03 rx-1 shorty and i weigh about 250. i paid about 170 for the spring and 1.5 hrs labor. it came to $270. also i am a very aggresive rider so with the stock spring i used to bottom out all the time which therefore i blew out the rear shock, so if you ride like i do i would get a hold of yamanator(fellow forum member) he knows someone who will revalve your rear shock to fit your weight. i would get these done at the same time since they have to pull the shock to put the fat boy spring in. but even with a bad shock that spring made a huge difference and make sure you replace the rear shock of the rear suspension, this is the one that matters for us big boys.
Mace