I built my Shredder II last year then spent the summer doing some trial runs and refining the buggy (plans are by ubuilditplans.com). Tore it down over this winter and had it sand blasted/powder coated, then back together. SO she is all done now and quite honestly is even better than I originally thought it would be! Put a factory new Honda GX670 with the governor tweaked for an extra 500 rpm. Probably about 26hp as she sits and unbelievable torque! Pretty much stuck with the plans other than the side body panels, larger fuel capacity, mud flaps on all 4 wheels and some add ons like GPS and such. I don't remember how many hours I spent on it but the better part of every weekend for about 5 months. BTW, if you build her go with the recommended suspension, worth every cent! Check out the video of her first run being a completed buggy:
http://www.youtube.com/watch?v=xxm5RM3lFB0