Out of interest, here is a picture of the BSA No 8 mounting plate as fitted to a .22 rifle with a suitable straight hand stock. There would be no point in fitting one to my BSA improved Mod D as in use it was necessary to remove the standard rear sight due to interference with the sight picture. Another associated accessory was "The Gibb Headrest" which was supposed to make it more comfortable when the eye was close to the eyepiece of the sight.
Brian