@Russ Black &
@mkao1248 have given sound advice. Ira is definitive. Your ODO is not used to calculate your miles, mapping software is. If Google maps shows your route, (using exact DBR locations), as over 1000 miles, you're most likely good. Still, there are proven reasons to have that 2-3% buffer, as Ira suggested. You don't need the Spot, and don't rely upon it to document your ride. Your job is to make it as simple and obvious that you did the ride you are claiming. The verification teams are not there trying to deny your ride, they and the IBA want you to succeed, but they can only use the documentation you give them.
If you need a few more miles at the end, sure, an out and back works, you're still on the clock and you still have to document that you did those miles with DBRs, not just your odo. You should have your entire ride planned out before you leave and know exactly how many miles it maps out to. So there really are only a few situations where you might fall short. Road closures/bypasses or you took a wrong turn somewhere.
Yes, the Ride around VA has specific cities you must get receipts in. As has been said before, and can't be stressed enough, you
MUST document any corner on your route required to prove you took the route you indicate with a DBR. If there is a shorter way, that's how the mapping software will indicate your path, and that's the mileage you'll be assigned for the ride. Remember, the DBR can be a computer generated receipt for anything, it doesn't need to be fuel. As long as it has the required info on it, it counts.
The verification team will not look at your spot track or your odo numbers first. They will plug in your DBR locations,
from the info on the receipts, and plot your route that way. If that number is good, and you met the requirements for the Ride around VA ride cities, their job is done. Make it easy for them. That should be all they need to do on a simple ride like this. If they have to go look at your spot link or start working to determine why your initial DBR calculated route is short of 1000 miles, you're slowing down the entire process and making more work for them.
Your physical condition has little to do with the ability to ride long distances. If this is the first time you've ridden 1000 miles, hopefully you have done other rides of 600-800 miles before and have some understanding of the dynamic involved.
Understand that while the Ride Around VA can be considered an In State Ride, you're only getting one certificate for that one ride. This is not the same as nesting rides. If you meet the requirements for the In State ride for VA, then your Ride Around VA will be listed towards your In State rides. As mentioned, you can't claim an In State SS1K ride and a Ride Around VA ride as two separate rides, it's essentially just the same ride, you
had to do 1000 miles for the Ride Around VA ride, arguably the more difficult one, in order to do the SS1K ride inside VA.