The inside face of one side of the valve slide has been gently cut back with a slitting disc, filed and had a thin coat of solder added.
To this, a length of 1mm x 1mm brass angle has been soldered in place. I've seen model locomotives where the valve rod jumps about because there is no restriction in the vertical plane, which this modification prevents, and you only need to do one side.
With the valve rod in situ.
The right hand cylinder block is almost complete now. The wrapper has no access cover as it is incorrectly placed on this side, so has been filed off and a new replacement will be made and added later.