Do not buy a Brooks B17 saddle for Strida because it cannot fit onto the plastic seat mounting.
Kelvin, the vice-chairman of HK Strida Club used to use a B17 saddle on his Strida before. Because the saddle could not fit onto the mounting, he cut off some part of the mounting to let the saddle to be fitted onto it.
However, after he has been using the B17 saddle with the cut seat mounting on his Strida for a few months, the plastic mounting broke suddenly during his ride. That caused him to fall down from his bike and got injured on his arms and legs.
Then, after replacing the broken seat mounting, he replaced the B17 saddle with a Brooks Flyer Special saddle which can be perfectly fitted onto the seat mounting of Strida.
So remember, if you want to replace your saddle, make sure it can be fitted onto the plastic seat mounting without problem and do not try to cut the mounting to adapt the saddle.