Larry,
I use my DFX on the beaches here in NJ and it works great. I use a modified RELIC mode as I like the mixed mode on the beach. I usually set the filters to 4 or 5, sweep speed around 7 and recovery speed 20 or so. I try to stablize the DFX to run at pre-amp 4 so I run the AC sens a little lower. I follow Jeff Fosters model in his book where you adjust AC sens lower to stablize. I run the DC sens around 48. I use the stock coil and the DFX does very well. Most times I switch to single freq 15kHz with VDI Norm off when I hunt the dry sand ( the VDI norm off gives me a better range of VDI's since there is alot of foil and tabs)...and if it does not chatter too much I use 15kHz in the wet sand, but if it starts getting a little un-stable I switch back to dual freq.
One thing about the DFX..you can really set it up to run smooth for almost any scenario and the VDI and Signagraph are one of the best visual dicriminators on any metal detector.
Hope this helps.
JC