[SOLVED] How to shrink BTRFS image

[Skywatch]

Hi,

I have been using a spare 64Gb card for xbian testing, but now want to move the working image to a 16Gb card. The question is how do I do that?

I have searched on the web but the rpi forums don't seem to talk about btrfs and I can't find a definitive answer to this problem.

I guess that btrfs filesystem resize 16:0g /mnt/tmp would work(?) but then how to resize the partition without grub or resizefs? The more I research the more confused I get!