Try contacting Allan Taylor (google 'Allan Taylor' and you'll get his website).

Allan was a great friend of Derroll and Danny, and at his gigs speaks of them both with huge affection. He wrote a great song about Derroll called 'Banjo Man':-

'Cowboy hat, cowboy boots,
Denim jacket full of Mexican cheroots,
How that man can sing "I've Got Trouble On My Mind"
I'm so glad that he's a friend of mine'

That's all I can remember, sorry.

S:0)