I've posted this same opinion a number of times so you may have read it elsewhere. At any rate, I've found the 4X6 coil to be very superior when coinshooting in heavy trash, the 5.3 is good as well, but I prefer the little 4X6. The 6X10 handles trash better than the 9.5 and has become my most used coil. If you hunt many trashy areas, the large coils are a real pain as they cover too many targets at once giving confusing sounds and info. I've hunted mostly in c/j mode, but after reading how some on the forum are having good results on coins in the other modes I intend to give that a serious try when the winter weather eases off here. For what it's worth as well, I've seen different trash items often ID as coins, especially foil and melted aluminum, but haven't had actual coins ID as anything but a coin. The false ID seems to be pretty universal with all TID machines, but with practice you'll soon begin to hear the difference in the signals especially if you also take time to X the target from several directions. In the end tho the only sure thing is to dig and eyeball the target. I have found that the MXT has helped me to dig less trash as I've learned its quirks. Have fun.
Bill