Remember , ALWAYS rebalance machine when adjusting power or preamp gain . Look for a preamp setting that is as stable as you can stand .. I keep at 2-3 on wet , but have went hotter on dry .
If I use the 950 I have no problem running RX15, at the beach depth is a big factor. Concentic coils false less in salt.
Ac sens i try a START point of 75 -77. I leave DC sens at 50 - 55 and dont really touch again.
The DC should have no effect in search unless you run MM or All metal.
You do need deep pinpointing at the beach so I think a higher DC would be called for.
A good all around VDI , i use is Accept + 69 to + 95 , reject - 95 to + 68
Most guys I know hunting the beaches want to find gold. rejecting the lower + VDI would eliminate gold.
I think I would set +95 set to zero.
Preinstalled programs are just a starting point , so your results will vary .
That is what makes spectra unique , is that you can create the best settings " out of normal "
Factory settings .
Also , +1 offset GB
Unfortunetly you will have your machine to you and your conditions .
Just as if you were using my machine you would probably not like my settings
Experiment .......