You can still do a circle route .. just go on past your original starting point to get the needed miles. A friend and I just did our first official SS1000 Saturday June 20th. We started in Eau Claire WI...if we would have come back to the same spot to end we'd have been about 5 miles short...we simply went on to Menominee WI giving us 1,014 total (GPS miles, 1038 odometer). It's all about having a start receipt for location and time, corner receipts to show your turns, and a end receipt with location and time...if you overlap a little bit of your route it's okay.
All the advice above is right on the money, plus this time of year is the absolute best time to do a SS1000...max daylight. I can't really add much to what's already been said other than make it fun! My friend rode his Royal Star Venture and I rode my FJR...he "thought" he was more comfortable and would pick on me at our stops; my FJR got significantly better gas mileage and I picked on him because we made two of our stops earlier than I wanted to (at least that's what I told him).
We started at 4:15 AM and ended at 8:45 PM, 16.5 hrs total time, 14.5 hrs riding time. We took decent breaks at each gas stop, plus a 1/2 hour for a lunch stop. But....relatively speaking our route was easy compared to trying to do elsewhere in the USA ... We started in Eau Claire WI, I-94 west to Fargo ND, I-29 south to Sioux Falls SD, I-90 east to Tomah WI, and then back on I-94 west to Menominee WI. Plus we had an added benefit of a 75 mph speed limit in SD, however some of the benefit was wiped out because of construction knocking the four-lane down to two for 50 miles plus. The weather was great (but we did go prepared for afternoon T-Storms) and traffic was light...I think St Paul/Minneapolis roles up the sidewalks Friday night/Saturday morning, I don't think we saw more then 15-20 cars on I-94 through the cities at 6 AM Saturday morning. While I-90 westbound was pretty busy, not much traffic on I-90 east. Busiest chunk of road all day was I-94 west from Tomah to Menominee to finish the ride out.
One secret ... lemon drops!
Good luck, enjoy!
Curt (07 FJR and 06 RS Venture)