Mine is an odd pair because the coil is hard to come by but my Deleon permanently has the Troy shadow super 7 coil on it. It's similar to the new 7" precision coil but I still find it special and better in some ways.
I had the coil rebuilt at Tesoro and then had my Deleon tuned to it. Like other non GB Tesoros, they run best with coil they are tuned to. You can use other coils but the further you get from the size and type (concentric/DD) the more off it can be. Plus the Deleon uses a hybrid of digital and analog and the GB is directly tied to the accuracy of the graph and the number scale. This is why the Cortes only let's you adjust the GB in all metal.
If you use a stock coil that it's tuned to, you can go to an 8" coil without many problems but going too much bigger or smaller can throw off the detectors outputs on the screen.
I settled on the "in the middle" of my 7" because I only use my Deleon to coin hunt and it's the best of both worlds. It covers more ground than the 5.75 and almost as much as the 8" donut and it separates almost as well as the 5.75. it's great on littered sites.
I haven't tried a DD on it, but I have had bad luck with DD and the bottle caps before on my other machines. If your ground isn't bad I would stick with concentric. The only upside to DD I've found is in bad soil because it "sees" less of the ground and minimizes the mineralization that the detector sees. In Michigan here I don't have bad ground. Concentric are also far superior on discrimination.
I agree with the above that the stock coil may be your best bet. I use the delta version of the 9x8 on my vaquero and modded Cibola with great results. However, I don't have the 5 pin epsilon "stock" 9x8 spider. I will say this. Besides the two versions of the vaquero and the tejon and Cibola being able to be purchased with either the 9x8 concentric or the 8x11 DD, Ihave found that the "stock" coils are chosen for a reason and should run very well with the detector. All my detectors run great with their "stock" coils.