I don't see why you want to use two stations, one after the other.
The AJS invisible stations can have a specified platform length up to 500metres, that's enough for 25 x 20metre cars.
To specify the length, place your station then click on the question mark at the bottom of the objects tab. Click on the station, select platform options then you can set the passenger shape, the number of passengers per hour, the platform length etc.etc.etc. The invisible track will change to match whatever track you are using when you join the track to it.
Cheers,
Bill69