So I've been using air disk on my Airport Extreme 802.11n, 100mbit model (pre-gigabit, pre-dualband). I now want to work at tweaking it for better AirDisk performance before I give up and go for the dualband (if that even helps performance).

Current setup-
* iMac 24" Snow Leopard & Macbook pro 13" Leopard (Snow Leopard soon)..both latest models running on 802.11n
* Airport Extreme 802.11n (pre-gigabit/dualband) running in 802.11n/g/n mode as I have a Wii & iPhones running in b/g space.
* USB2 Hub connected to AP Extreme, to which I have 2 USB2 drives plugged in. Both are HFS+ Journaled.

Initially I was seeing 1-1.25MB/s write speed. (bad)
So I ran some WiFi scans and moved from Channel 1 to Channel 11 as my neighbors had strong signals on Channels 1,6,7.
Now I am seeing 1.25MB/s-2.8MB/s, but really its all over the place in that range. Even 2.8MB/s is not that impressive.

I've read that disabling journaling on USB drives can double performance. Is this true? What are the downsides?

Dual band
Does the new model, dual-band, allowing the 802.11n clients to live @ 5gbz spectrum really make a big difference in throughput?

USB hub/multiple hard drives
Does using a USB hub impact performance at all? I've read that Apple recommends using a USB hub for bus-powered disks on the AP Extreme.
Does having multiple disks on that USB hub impact performance during non-simultaneous use?
When I ran testing I was only accessing 1 drive at a time. Clearly accessing both at same time would result in a performance hit, but what about just having them both there, idle?

Snow Leopard
Has anyone seen performance improvement/degradation on upgrading to Snow Leopard?

If anyone has performance numbers on their setup, it would be greatly appreciated.