[Q] DS20+KZPAC+BA356 installation issue

Dear all,

I have inherited a DS20 with a three-channel KZPAC controller (a.k.a. 
Mylex DAC960) with the following setup using the internal disk bay:

2x 9Gb in a RAID 1
4x 9Gb in a RAID 5

This works wonderfully well and a recent Linux distribution 
(Debian/sarge) happily runs on it.  I have now been asked to connect a 
BA356 to the box which houses 2x 9Gb and 4x 19Gb disks and my cunning 
plan was to use the external connectors at the back of the KZPAC to 
connect it.

After digging through my memory (it has been a long time since I last 
installed one of these babies) I recalled that there's an issue 
regarding how the buses are split on the KZPAC and in particular on the 
DS20 the built-in disk bay is actually not on a single SCSI channel but 
split over two channels.  I also checked in the KZPAC manuals and the 
two connectors at the back are channel 0 & 1 respectively basically 
extending the internal buses.  The other spare internal connector on 
the KZPAC is channel 2 which can be "pulled" out via a suitable option 
which I don't have...

The BA356 is also in split-bus configuration, i.e. there's two SCSI 
cables coming out of it and if I connect it to the KZPAC directly and 
try to bring up the system I get a failure on the internal disks losing 
disks 2 & 4 (counting from 0) on the internal bay and disks 2 & 4 
(again counting from 0) on the external BA356.  That indicated to me 
that there's an obvious SCSI ID conflict which is to be expected given 
the split-bus configuration on the DS20... I can see only three disks 
(1,3,5) but can't see 0 at all for some reason (might be dead, green 
light is on though but the KZPAC management s/w can't see it).

Note that the KZPAC sees all the internal disks as the first column 
(channel 0) so I might be talking totally out of my backside on the 
DS20 split bus and the issue is "simply" one of setting the BA356 dip 
switches to turn it into a single channel and then stick that into the 
external channel 1 port (where it sees the three disks in the BA356 
already). I _think_ I have figured out where the dip switches are via 
the BA356 user's guide  found via Google but any further guidance or 
caveats would be greatly appreciated).

So, my question to the gurus is which is my best course of action at 
this point bearing in mind that ideally I wouldn't want to reinstall 
the whole system (it is running as an Amanda backup server with an SDLT 
and doing a very fine job but needs some extra staging space)?

To make matters more complicated I only have a remote serial console 
via serial concentrator onto the box with a pair of kind but totally 
unexperienced hands on-site.

Thanks in advance.

Ciao,

Arrigo