bought a 4th roller for my 8f . the new style are taller. the nice dts man, offered to modify my existing 3 rollers to match. now i have 4 taller ones, i had to the renew the bed of the rolling road to suit. i picked some off cuts of 12mm ply yesterday for under £3 at the timber merchants and started to glue the upper section to the main bed. hope this interests you to do similar. rollers can be obtained on ebay or from directtrainspares-burnley.co.uk
https://www.youtube.com/watch?v=adxUHYAHNq0
if you happen to have a full set of the original sized rollers and would like my old bed, minus cliff barker track, you are welcome