Hello blund301,
I know the V3i has a dedicated prospecting program. I don't own one. I assume when the prospecting program is employed, it would put the machine in all metal mode, using the highest single frequency, not multi.
Generally smaller coils will work with small gold better. Won't go as deep. In most locations sub gram gold is what is found, not huge nuggets.
Concentric coils tend to be more sensitive, but, are less effective in harsh ground. The DD coils handle bad ground better.
I have a GMT a totally different animal than yours! I can't help with any customized settings therfore.
Hopefully, someone who uses, or has used a V3i can help out. To my knowlege, the V3i isn't one of the more common VLF machines used for nugget shooting.
GOOD LUCK