The eminent Mr. Condelli mentioned

>>calculate the
drain on the battery and find the size solar panel that will keep  the
charge up
for the 6 hours without sunlight on those Mexican beaches.
<<

I suspect the requirement is a panel that will deliver enough charge to add
X ampere hours worth of 'power' over the day to keep his equipment on line
for six hours.  Almost all the solar panels I've looked at don't do much
without sunlight ;)

Also keep in mind that the rated power is not the 'real life' power for
these arrays.  If can get the efficiency specifications for the array versus
output voltage.  Some arrays as Matt R. mentioned have varying efficiencies
depending on voltage.

Sunsei is a manufacturer that makes flexible solar panels for a very dear
price.  Some can be found online.  They're handy, can be paralleled with no
extra wiring, weigh little and stow efficently.  They're about 10-20 dollars
US per watt.

Old guys and TDIs rule!  The crusty vets from AUDI Sport took Le Mans with
Peugeot TDI power second in P1.  GT1 had an Aston Martin DB9-R 'eeking' out
a win over the one remaining GM Corvette in the race.  David Brown would be
proud to see tractor power do it again.  Carroll Shelby drove an Aston
Martin to victory long years ago.

They were referred to as the pensioner team.  I liked that.

pensioner