In our team, we never strung it at 20 ... at least 23 cross 24 main. As long as you dont string it above 25, it should be ok.
This has been discussed and I'm sure a search would find the thread but I'm not sure what you'd put in seach! What Yonex recommends, you don't have to follow. The recommendations are a "safe zone" so they don't get too many breakages but try to keep the level of tension high enough for players to stick around. Other than that, take a read at this: http://www.badmintonforum.com/vb/showthread.php?s=&threadid=7884
Yes, it has been discussed before. MP100 can definately take tensions of up to 25lbs. My friend even strung his once at 29lbs if I'm not wrong. Oh his was the CP version FYI, just in case you intend to string it at 29lbs...
thank you for your prompt replies. i'm sorry i didn't use the search function before posting. the tension of my racket now is 22lbs but i intend to change it to 24lbs.