Hate to confuse you mate but I am using the 14x9 ( if Dan ever lets me out again) and have found small gold with it. While I would have found it with the stock coil, you get much more ground cover with the bigger coil and one day I hope to dig a slightly deeper hole and find my first gram size piece.
While I have been locked up made myself a new hipstick and cant wait to try it out on the goldfields, come on Dan give me a break.
Cant hurt to have both coils if you can afford to.
Cheers
Bob