Hi Pete, I took a Gliding Proficiency course at Catterick in the early 60s. I do remember those trailers you describe being designed for Cadet IIIs which we used in the second phase of training. During the first phase using Sedberghs they were usually ground handled (pushed!) but on occaisions when expediency was required the trailers were pressed into service to take the weight of the aircraft but they were never secured to the trailer and balanced using a wing-walker. Were the trailers modified to properly accept Sedberghs later?