The smaller coil will find the smaller nuggets, but at a lesser depth then the 8.5 x 11. The 8.5 x 11 will find larger nuggets at greater depth. So, you lose something and gain something with either coil.
Personally, I would go with the smaller 5 x 7 coil on the Max, in true all metal mode. Chances are, there will me mineralization in gold bearing country, so the 5 x 7 coil will be able to be run at a higher sensitivity level. Plus.....there are more smaller pieces of gold out there then large nuggets. One final option, if by chance you are in a virgin area......clean out all the smaller pieces of gold with the smaller coil, then switch to the larger coil and get what's left.
Sounds like a great trip!