You'll need to enter in a custom range, try the one below
pclock 5-90
hclock 15.1
vclock 50-60
then select easy centering and adjust the hight to 224 lines (shift k). You'll probably need an ati rage 3d, or an ATI 128 Pro (recommened) to get such a low pclock.
the default 15.75 would put your setup at
240x60=14400
14400/15100=.953
95.3% is really high, probably undoable.