25 miles is totally doable, in fact it's done. Just think of it that way. it is less than 2 hours cycling, and for some it's about an hour, but I doubt you are that fast yet. I know you have screws, so taking it slow and steady will be the goal. I'm over 200lbs too, however I suspect my body composition is a bit different than yours. cycling can be harsh on big riders, because you get the impression that everyone is a weight weenie. but that's not the case. google "toast bread with bike" and tell me that guy is a lightweight lol. don't get discouraged. just ride, and ride longer. at this point I can put down 10 miles in just over 30 mins. shoot to ride longer say 2 hours, and the 25 mile ride will fly by. you can do it!!!