Errrrrrmm.....11s are 'extra lights'.

Personally, the absolute lightest string I'd use on an acoustic would be 'Lights', 12-53 or 54. I have those on the Lowdens. Anything less is just too 'weedy' in both sound and feel, AFAIC.

On my Martin Dreads, I always have 'Mediums' - 13-56. A Dread needs Mediums to drive the top.

The usual disclaimers apply......IMHO, YMMV etc.