I've generally found loads on a long line less inclined to spin than those on shorter lines, although a pendulum swing is then more likely.
Back in the 70s at Boscombe, we did some trials with 'jungle penetrators', heavy, anchor-like devices with strop attachments for crew and SF recoveries. It was attached to the underslung hook on a 300' nylon rope, with 3(4?) dummies attached. Took them out on the Plain and tried increasing speed points. IIRC, we got to 40 kts (load now trailing way behind the t/r) and the load and rope developed what I can only describe as a 'sinusoidal whip'!!
Shortly thereafter, it went solo!
Not too enamoured of the principle but, I suppose if the baddies are after you it MIGHT offer an option ... but then again!!
