I'm strongly considering doing a Saddle Sore (IronButtAssociation 1000mi in 24hr) ride sometime next spring (deer on the roads at night, fall and winter have longer nights obviously, spring gets the right amount of daylight and the lowest heat).
I have done several 300+ mile rides at one time and didn't notice any discomfort what-so-ever, and over half of that was at speeds over 75mph.
I've got my cert and a 1000 is a WHOLE NOTHER BEAST than 300
It's a whole other beast than 750!
I'll give you some tips now. First hydrate, wear a camelback and use it. Route choice, plan on leaving in the early AM to finish in daylight if at all possible. You don't want to be running after dark after doing close to a 1000 miles. If you can, choose a route with as much interstate (higher speeds) as you can and avoid major cities and construction. Stops will make our break your attempt. Practice them before you attempt. Same thing for doing miles. You will have a VERY tough time if you try to go from 300 to 1000. Do 500 and see how you feel. Then 750. Any slight soreness or aggravation you notice at these distance will become MAJOR obstacles after 15+hrs in the seat.
Read, learn and practice the IBA's words of wisdom (it's a link on there page).
The trick, and believe me, it is a trick to doing big miles, is "sit there, twist that". If your not moving, you losing. Those 10 minute rest breaks every hour will do you in. Better to be the tortoise than the hare.
Don't be afraid to bail out! It's easy to say you will, but believe me, it takes real cajones to abort an attempt.
Their is no way in hell I'd try to do an SS1000 on the CBR. But if you pull it off. Beer is on me!
I'll be pulling for ya!