Intriguing project there Freddy.
I was thinking a rack & pinion design might work sweetly for sliding out your outrigger arms, one less hyd valve & cyls.
Did you see Krys's knuckle boom trk, he was using a nifty fork cradle for no hands on to load/unload the freight.
http://www.youtube.com/watch?v=zUoSMk-4-ow
(starting @2 minute mark)