I doubt there's anything wrong with the suggestion your dealer makes, but Blue-tac will be better, and easier.
Also, there's an Audiogonner who has suggested Artist's putty is better than blue-tac - maybe try it if you can't get blue-tac.
Also, there's an Audiogonner who has suggested Artist's putty is better than blue-tac - maybe try it if you can't get blue-tac.