I think that Martin says inside - medium strings. The dreads are designed to be driven by mediums.

I play with a cross over strum and finger style so light gauge strings are my choice. I use 80/20 lights on my JC 16 because they are kinder to the fingers and my fingers need kindness. If I need volume I turn it up. I use Martin Bronze lights on my Guild F-30 because it is 50 years old. But the Guild sounds great so why change.

GHS strings don't seem to last for me. It's a body chemistry thing.
But with a long neck five I am stuck with GHS strings for he banjo. Thats what I have available with out going mail order.

D