Carbines I've had:

Ruger 77 RLS 30-06 (18.5")
Ruger 77 RS 358 Win (19")
Ruger 77 RL 257 Rob (20")
Ruger 77 RSI 308 Win (18.5")
Ruger 77 RSI 7x57 (18.5")
Ruger 77 RSI 250-3000 (18.5")
Winchester 70 SS FWT 308 (19" w/ open sights)
Winchester 70 SS FWT 30-06 (21" w/ open sights)
Remington M7 SS 308 Win (20")

All that to say I'm not exactly a stranger to the concept... depending how they balance, I really like them, apart from the M7. Still, I'd not go shorter than 20" anymore, depending. Short barrels are LOUD. And I always thought the Ruger RSI should have been made with a 20" barrel.

Still, I'd not cut a Kimber 84M MT below 21", maybe 20". I'd bet the balance would be lost in that light rifle below that length.

“Perfection is Achieved Not When There Is Nothing More to Add, But When There Is Nothing Left to Take Away” Antoine de Saint-Exupery