When you set up short nosed saddles, there's a few thing you need to do. In an ideal world a saddle fit helps
1: measure your old saddle when it's on the bike, to where the width is 7cm and mark with a piece of tape. This is the centre of all saddles
2: measure from the tape to the centre of your bars or top cap and take a note of the measurement
3: measure to the centre of your short nosed saddle
4: set up your new saddle to the same measurment form the bars/top cap
I hope that makes sense
Also get a good pair of shorts