swap partition

[Stari Karp]

Hi!

I like to increase swap partition but I am scary to screw up my system.
FreeBSD is installed on iMac (Mountain Lion).

gpart show
=>        34  1953525101  ada0  GPT  (932G)
          34           6        - free -  (3.0K)
          40      409600     1  efi  (200M)
      409640  1216587112     2  apple-hfs  (580G)
  1216996752     1269536     3  apple-boot  (620M)
  1218266288        1024     4  freebsd-boot  (512K)
  1218267312   727710720     5  freebsd-ufs  (347G)
  1945978032     7547102     6  freebsd-swap  (3.6G)
  1953525134           1        - free -  (512B)

What I planning to do:
Boot to OS X and than decrease apple-hfs partition for 64 GB.
Than boot to FreeBSD (single user) and:
swapoff -a
gpart resize -i6 ada0
swapon -a

Do I need to use gpart resize -i6 -s 64G ada0 or gpart will find empty
space and use it, please? Should I format on OS X empty space to FAT?

And I am using rEFiT for boot manager.

Thank you.

SK