Following on from Paul Rushmer's suggestion:
In LBSC's book "Simple Model locomotive Building introducing LBSC's TICH" there is a frontispiece photograph showing Curly's own version of "Tich" which is a 3.5" gauge tank engine similar to Juliet. It is shown pulling the wagon devised by LBSC to carry additional supplies of coal and water as well as fireman's tools. The wagon is a traditional 5 plank coal truck which looks the part but there are no plans for it in the book.
I could let you have a scanned copy if this would be of interest.
Regards
Dave

LBSC's design for his 'trailer wagon' for Tich is covered in Model Engineer magazine, 2 April 1959, Vol 120, Issue 319, pages 414 – 416 & 423.

There is a general arrangement drawing, and reduced detail dimensioned drawings of underframe, 'tank' (body), wheels, buffers, axle-boxes, etc., accompanied by a descriptive construction text.

Regards,

Phil