Pastor,one thing that kills people when using a substantially smaller coil is the fact that you can't cover the same amount of ground in the same time. People inherently want to go fast,but this is a situation in which "fast" isn't good,especially in areas which you've determined to be "trashy". The term "trashy" means different things to different people,but if you cannot make any sense out of the site with your bigger stock coil....go small! The Blue Max will go deep,but don't worry about depth in heavier trashed out sites,the upper level garbage won't allow the IDX to see something under it anyway for the most part. Don't get me wrong,I LOVE my IDxPro(observe my name). But it's not a magic wand. With the small coil on it you might start to think it is though! Be thorough,hunt methodically,keep an eye on that meter! Dig anything in the upper 3 segments,and if it hits at zinc but pops over to 1c/10c once in awhile,dig that too! Make sure your ground balance is optimized if you have bad dirt and don't be afraid to use some disc to knock out the iron and foil. If you're coin hunting ONLY and aren't worried about nickels,just set the disc to P/Coin range.
The small coil will blow your mind with its separating abilities,but you have to be willing to work a smaller area for the same given amount of time.
I'd say "Good Luck" but it won't be needed...all of your "luck" is in that little coil.