Originally Posted by
pacificaslim
If he has to use a 90mm stem he's already bought the wrong bike. Or has very weak core muscles.
There is a wider range of seat positions that do not trouble the knees than the KOPS staring point advice leads people to believe. The seat should be set so one's weight is supported by his legs and there will be no need to place any significant weight on the hands.
Its a flat bar bike, there's nothing abnormal about a 90mm. The mountain bike community 40-50mm stems are relatively common on mountain bikes.