CGBD: Have I got the right notes compared to GDAE tuning.

D = 5th fret on A string
B = 2nd fret on A string
G = 5th fret on D string
C = 5th fret on G string

If that's the case, I would guess:

Standard mandolin E would tune down OK to D
The next 2 strings are only 1 tone either side of the A string - probably an A string would work either way but may feel a little odd
The D string would tune down to the C

I haven't got a set of mandolin strings to hand but I've tried to find some gauges.

I'll throw 10, 12, 15, 26 into this as a suggestion (I could be way out) and see what others think or come up with.

Jon