With everything I have read up to this point...I would have to advise to just get the 11 inch DD coil for your new Gamma when you get it. What I have heard is that the SEF "can" give an extra 1 to 1 and 1/2 inches. You "can" get that over the stock coil with the 11 DD. I personally did not see the extra depth in air tests between the stock coil and the 11" DD coil, but I could only test at a sensitivity of 92 out of 99 because of EMI in my house. I have heard that the SEF coil is pretty heavy compared to the DD, which throws off the perfect balance of the detector. If you are planning to use it in local parks in your area, I would highly recommend that you get the 5"DD instead. It is phenomenal in trash and target separation, and the Gamma has a very quick recovery speed. I have dug coins up to 7 inches with the 5 inch coil. Much deeper than you would expect from such a small coil. I am reasonably sure it will go a little deeper, just haven't put the coil over that target yet. The 11 inch DD does just as good but will work YOU a little harder trying to isolate a single signal in a trashy park, so it is better for less trashy areas.
Understand that I have NO personal experience with the SEF coils, just research. Hope this helps in your decision.
capt1989
