maybe you don't hit hard so that there are no problems with your racket. It is indicated on my racket 18-23lbs. I strung mine @22lbs because at 23lbs, myracket would probably break if I hit hard or took a rim-shot.
oh sorry.mine's an mp27.no wonder the tension recommendation is different. ps:i CAN hit hard.my level's at 28lbs =)