Had a try of the 15" dd on the trusty old 3500,ran it in sensative and deep,both mono and dd settings,super stable in both,didn't get any targets,so can't say about depths,didn't get a chance to to swing over some heavy mineralized ground,but in the mild ground it ran sweet as,so I can imagine it would be great in the heavier ground,deffinatly a good purchase for the gp owners out there