Inserts on a mount

[evert]

I just wonder if these inserts would hold the scope firmly enough in a springer (even a well mannered one as mine are) Could anyone who has used them give an opinion please?

I made dad some delrin inserts to use a 26mm scope with 30mm sportsmatch mounts on his modern synthetic sealed HW35.
He has not mentioned any problems, but the again, his HW35 isnt the hardest recoiling springer.