Hmm,a B4 spur,I'd go for about an 81-82t and a 22-23t pinion with a 27t stock.
Did you use standard B4 pads with it?
What dimensions are your PTFE slipper plates?
The lad can get his mitts on PTFE round bar and they have a lathe
where he works so I might just be on to get him to make me a pair.
Though knowing him,it'll be like trying to get blood out of a stone
Edit.
Just asked the lad about PTFE round bar,he says they threw it out a few
months ago because no one used the stuff anymore,groan!!!.
So that's that plan buggered,rats.
Mark.