String Gauge question.

[Jimbo]

I've recently discovered that acoustics can sound quite nice when standard tuning is dropped by one whole step making the tuning DGCFAD.

The trouble is that the strings are a lot slacker. What gauge of string would you recommend to get the same string tension as 12's in standard tuning? Would 13's do it, or would you need to go heavier again?

[JB]

13's would be a good test but it can vary depending on the make of strings too.