MSV website says:
Bedford Autodrome: All circuits Daytime and Evening - 101db
Bedford Autodrome also has a 87.5dB(A) drive-by limit which is measured at a distance of 20m.
See https://car.msvtrackdays.com/FAQ/Booked?utm_medium=menu
Graham,
Turn 7 recently did a YouTube video about aero screen fitting. I think they discuss the retaining channels. https://youtu.be/R9qkqxHmkTQ?si=kjkXexrJ6Tg0quEZ
Cheers,
Mark
EDIT Just noticed that Benton has already linked this video. Oops.