CA just beat me - Have you got any rides under your belt longer than 43 miles? Such as 60 or 75? That will give you a better idea of whether you can make it. You can then push through the last 20 or so.

50 and 100 miles are different animals.

Although I hear people do the jump, it's your confidence we're talking about, and you just might suffer. As in really sore legs, and sit area, having to crank out another 30 miles.

There's always next year.