My supplier doesn't have them in yet so went for the 3900 , hopefully same and more features

Which fiber module does the 3900 take ? Where to get one for the LAN Side to HP procurve Fiber module ?

Well I've got to give Draytek credit. They now logged on remotely made some changes and the end result sadly is still no fix.
So load balancing doesn't work for me or for them.
The next firmware update is going to be fairly important by the looks of it.

GhostWorks wrote: Which fiber module does the 3900 take ? Where to get one for the LAN Side to HP procurve Fiber module ?

No idea I don't have 3900.

I only had a quick go at load balance for my 2 WANs , didn't work, will give it another go tomorrow ( Vigor3900)

i followed the user guide as went fine for load balance...

I set up to 2 x Lan's ( LanA & LanB )

LanA to use WAN1
LanB to use WAN2

if either wans fail it will use other wan ...

Seems fine