GDAE is the preferred tuning for playing melody, GDAD for accompaniment.

Because I play in both tunings, I tune my zouk FCGD and use a Kyser mandolin capo at the 2nd fret. This gives me GDAE when I put the capo across all four courses, and GDAD when I leave it off the high strings.

What brand did you get? Mine's a Davy Stuart (from NZ).

I highly recommend that you join the Yahoo Cittern group. Lots of knowledgeable folks there including professional performers and luthiers.

Cheers,
Michael