His size (5' 7") is one of the three things to which 'Winkle' Brown attributes his survival:
“Firstly, I prepared myself very, very carefully for every flight. Secondly, my size worked in my favour – in the Swallow, in the crash of an Me 163 at Wittering and in other cases, I would have been killed, or at least lost my legs, had I been taller. Thirdly, there’s a small element of luck, whatever that is.”
Interesting interview here -
Profile: Captain E M Brown CBE AFC DFC FRAeS RN
It starts at page 8 of the link.