So I unbridged between #4 and #5, going back to four chips, and it's back to fast:
cgminer version 3.3.1 - Started: [2013-08-29 05:42:33]
--------------------------------------------------------------------------------
(5s):10.56G (avg):9.477Gh/s | A:160 R:0 HW:0 WU:132.4/m
ST: 2 SS: 0 NB: 1 LW: 251 GF: 0 RF: 0
Block: 002f2d30baf48c98... Diff:65.8M Started: [05:42:33] Best share: 360
--------------------------------------------------------------------------------
[P]ool management Settings [D]isplay options [Q]uit
BITFURY 0: 11.61G/10.63Gh/s | A:176 R:0 HW:0 WU: 148.6/m
--------------------------------------------------------------------------------
[2013-08-29 05:42:26] Started cgminer 3.3.1
[2013-08-29 05:42:26] BITFURY chip #1 detected
[2013-08-29 05:42:26] BITFURY chip #2 detected
[2013-08-29 05:42:26] BITFURY chip #3 detected
[2013-08-29 05:42:27] BITFURY chip #4 detected
[2013-08-29 05:42:30] BITFURY: 4 chips detected!
Next, bridged 4 to 5 and unbridged 5 to six:
cgminer version 3.3.1 - Started: [2013-08-29 05:47:30]
--------------------------------------------------------------------------------
(5s):9.923G (avg):8.487Gh/s | A:184 R:0 HW:0 WU:118.6/m
ST: 2 SS: 0 NB: 1 LW: 379 GF: 0 RF: 0
Block: 0034005b153db46a... Diff:65.8M Started: [05:47:30] Best share: 1.52K
--------------------------------------------------------------------------------
[P]ool management Settings [D]isplay options [Q]uit
BITFURY 0: 10.17G/8.956Gh/s | A:192 R:0 HW:0 WU: 125.1/m
--------------------------------------------------------------------------------
[2013-08-29 05:47:23] Started cgminer 3.3.1
[2013-08-29 05:47:24] BITFURY chip #1 detected
[2013-08-29 05:47:24] BITFURY chip #2 detected
[2013-08-29 05:47:24] BITFURY chip #3 detected
[2013-08-29 05:47:25] BITFURY chip #4 detected
[2013-08-29 05:47:25] BITFURY chip #5 detected
[2013-08-29 05:47:28] BITFURY: 5 chips detected!
slower!