repairing broken Mk3's
The MGSP knew what they were doing, but in actual fact the number of 'broken' machines in the system was very few when one considered the large number of real training flights (leading to solo) completed. The jolly old 'wheel box' area was the usual suspect and not just from a heavy arrival as the grass could conceal unhelpful objects that could cause damage. Most of these 'repairs' were done at the schools when the team in their 3 tonners visited. The aerolite was cured by simple 'bulb heaters' made out of plywood.
The MGSP guys would have easily adapted to 'glass' because they already completed scarf joins in ply and 'extending' the scarf ratio would have been an extension of their normal skills.
When I attended SM for a course there were no actual broken airframes to practice repairs on (such was the low rate of attrition) and so the guys would repair ply cabinets from the billets.
WE forget that before the schools were actually 'tasked' for AE work most ATC glider flights were dual training for the A&B, therefore it only enhances both the suitability of the equipment, standard of training, sturdiness of the fretwork fighter, and the overall fantastic volunteer organisation not hindered by crats. I am not sure when the T21 started to get its nose weight mod, however there were a few around that were original and had certain 'light pilots' limitations. Not for long at Kenley; a local mod saw a lead seat pan made and kept in the caravan ready for use.