Back when we had such a unit, the School of Refresher Flying used to get very hacked-off with the number of pilots who arrived from North Luffenham with a helmet so tight that flights were often terminated early due to the pain suffered by the refresher student.
The Squippers' helmet testing rig was frequently mis-employed as a 'helmet stretcher', which helped a bit. But the fault was with the Luffenham chamber-minders and their quackery insisting on ridiculously tight fits.
I was at Luffenham doing my pre-Vulcan AMTC course when Tim Webb and the late great 'Puddy' Catt turned up having flown over to Wittering in the Brawdy Meteors after having been pinged for a 'mid-tour AMTC refresher'. I told Puddy that I was surprised at the immaculate condition of his bonedome, to which he replied "I don't use it for flying, old boy - it's one I've acquired just to keep the docs happy! My comfy one is sitting safely in Winston's cockpit!".
Typical Pud!