How much difference is there between the 11" DD vs the F70 stock coil? When I try to do tests with my F70 inside the house the electrical interference makes the F70 really unstable that I have to cut the sens and threshold way back. Will the 11"DD help out with this problem? I have read posts where the Minelab explorers are really stable machines and will pick up a coin really close to an iron object, can the F70 with the 11" help do this? Thanks for any advice. HH