“Madder than a sackful of ferrets” (very mad)

“Mad as a ferret” was printed in the Daily News (New York, NY) on February 19, 1971. The expression possibly borrows on the older “mad a a March hare.”
 
As mad as one ferret is, several ferrets in a bag or a sack are even madder. “As mad as a bag of ferrets” was printed in The Sunday Telegraph (London, UK) on April 17, 1977. “HOLLYWOOD women - mad as a sack of ferrets” was printed in The Sun (London, UK) on June 26, 1998. “Madder than a sackful of ferrets” was printed in The Guardian (London, UK) on September 25, 1999.
 
     
19 February 1971, Daily News (New York, NY), “The Latest Wuthering Heights Adds Up to Moor of the Same” Rex Reed, pg. 60, col. 1:
In the new version, young Timothy Dalton looks mad as a ferret, but there isn’t much emotion in his Heathcliff; ...
 
15 August 1977, Newsweek (New York, NY), “The Sphinx’s Lair” by Margo Jefferson, pg. 76, col. 2:
Is she really “mad as a ferret” or just a clever actress?
   
17 April 1994, The Sunday Telegraph (London, UK), “The Arts: Flying over the edge: Cinema” by Chris Peachment, pg. 6:
...was deeply repressed and she was as mad as a bag of ferrets.
     
26 June 1998, The Sun (London, UK), “Hollywood babble-on” by Ally Ross, pg. 4:
HOLLYWOOD women - mad as a sack of ferrets.
     
10 April 1999, The Daily Telegraph (London, UK), “Peterborough: Fuming” by Simon Davis, pg. 23:
The latest example of the state’s madder-than-a-van-of-ferrets attitude to smokers can be found at the Ahmanson theatre in Los Angeles, where the ballet stars Adam Cooper and Sarah Wildor are appearing in Cinderella.
 
25 September 1999, The Guardian (London, UK), “This Sporting Life” by Harry Pearson, pg. A12, col. 6:
The Olympic boxing judges, meanwhile, have shown themselves madder than a sackful of ferrets time without number.
     
Google Groups: alt.fan.scarecrow
Footie thoughts
Jon
1/4/01
(...)
There’s more talent in his feet than in a lap dancers’ dressing room,  he’s got comedy stick-on-style sideburns, looks like Frankie Dettori and “best of all - he’s madder than a rabbit in a sack of ferrets.”
   
Google Groups: uk.games.video.dreamcast
Bangai-O….Maddest….Game….Ever
Marcus Gray
1/31/01
(...)
It’s as mad as a bag of ferrets.
     
Google Groups: uk.games.video.dreamcast
Stop the insanity!
Marcus Gray
8/2/01
Just got the new Treasure game ‘Freak Out’. Brilliant!! Of coarse being Treasure it’s madder than a bag of ferrets.
 
8 September 2001, Sunday Business Post (Cork, Ireland), “Fiat Multipla vs Chrysler PT Cruiser,” pg. ?:
Looking from the outside, this MPV looks as mad as a bag of ferrets.