I think they mount to the waist belt, not to the back plate.
They should have a slot or loops to thread on the belt.

BUT...

These may be Halcyon's finest example of overly complex engineering.
If the dealer will take them back, I suggest you do so.  Purchase
some simple pockets from DiveRite or Halcyon -- often called
"trim weight pockets" or something similar.  
Cheaper, smaller, simpler, better.  The "K.I.S.S." principle.

I currently dive with 8 lbs.  I have two pockets on my waist belt
and two more on my uppper cam band.  2 lbs in each of these, but
I could use up to 5 lb weights for a total of up to 20 lbs --
although I'd not expect to need nearly that much.  

This setup gives me both proper bouyancy AND proper trim.  
Half the weight is readily ditcable, which is plenty.

If you are diving in situations where more weight is required,
I suggest you use a seperate weight belt.

The best way to mount them is to mount them in a package and send it back
for a refund.  The Halcyon ABC system is possibly the worst product they've
every marketed . . . except perhaps for the soft keel weight.

If you're not willing to take that advice, then yes, I know how to mount the
system.  You thread it onto your waist strap, one on each side.  The right
one has the strap and buckle on it.  The left one goes behind the D ring on
the left side.  As I recall, there are a couple of holes in the units for
attaching them to plate.  I don't remember whether they are straps that go
through the slots or holes that are attached to the holes in the plate.
Either way, it should be pretty obvious.

Lee

The back of the pouch mounts to the corner holes in the BP, as it's
threaded on the waist belt. While I'm not a huge fan of the system, it
worked pretty well when I dove wet, but I've since sold them.

Laser

Thanks,

I was just confused, because the straps seems to be long enough to go
through the slots (where the harness is fixed) and back again, and then be
bolted to the plate. But if you do that, then there is no room for the
harness, so I was wondering if the Halcyon BP had extra slots for the ACBs.

Anyway, I'm lookin' forward to get rid of my belt :-)

-Henrik

I use the Zeagle ZipTouch Weights / Backplate.
They can carry 20lbs(10lbs block slips right in) , bolts to the backplate
and slip onto the harness.
I have tried several other models, but these a holding the weights "upright"
so they leave room for both canister and d-ring.
easy to release and "refill". Best i have tried yet.

just my 25

Happy diving
Tommy
www.scubagear.dk

Henrik,

I have to agree with Lee Bell here. Although Halcyon makes some
excellent products, the ACB is not one of them IMHO. There are other
ways to add ballast to your backplate and wing setup that are better
and don't cost nearly as much.

I use a stainless steel backplate for diving wet or dry which gives me
about 6 lbs (~3 Kg) of ballast. For warm-water ocean diving, I only
need a few more lbs of ballast. If I'm using a canister light, that
gives me the additional weight I need. If not, I use a weight pouch
where the canister would have been on the waist belt on the right.
Both of these solutions are easy to ditch in an emergency and provide
enough ditchable weight to have a balanced rig. A simple weight pouch
that slides over the harness waist belt is very inexpensive.

For cold-water diving, I always use a shell drysuit. For additional
ballast, I start by adding one of Scott Koplin's excellent weighted
single tank adapters, which adds another 6 lbs. Any additional weight
needed can be added as JOR suggested with weights added on or around
the tank.

To me, the ACB just adds drag and complexity that you don't want or
need.

-bob