Hi Dog -- I did the Flying Wheels Saturday with only about 400 miles of outdoor riding under my belt since January (yikes). I was really worried about how I would do with the utter lack of riding I had done, but I finished stronger than I have ever felt before, largely due to the increased amount of indoor training and spinning classes I have taken. I have done the STP 6 times, 4 in two days and the last 2 years in one day. I have always used Flying Wheels to gage how ready I was, and I am feeling more confident than I was before Flying Wheels. The one day stp is definitely harder only because of the shear fact you are on the bike for 13+ hours. There aren't nearly the hills as Flying Wheels, but I think the hardest part of the one day stp is mental. No matter what, when I hit mile marker 170 around the St. Helen's stop I always wonder what the heck I am doing this for, but coming into that finish line in Portland is soooo gratifying and knowing I don't have to get back on the bike the next day is sooooo sweet! Just pace yourself and I think you will do fine.