my mate had a first cross fell x whippet and i can honestly say its 1 of the best alrounder i have ever seen working. he died last year while out doing what he loved. but not all's lost my mate putting his first cross beddy x grey (heartbreak fell) dog over the fell x whippets litter sister to get the blood back before its lost. id say that other terriers can be used people just stick to what they know and what works for them