if you go numb with 13 minutes of riding, you need to stay off the bike until you fix that problem... that's not good for you... just keep trying hard, don't worry terribly about position, position is for the pros or the very fast amateurs, and you are neither.
If you're not swearing like a sailor the second you cross the finish line, you're doing it wrong.
what about unable to speak a word, face covered in spittle and snot?