Tandem as cargo bike

[fruitcake]

Ideas on how to do this, please.
The tandem is hanging in the utility room (never particularly enjoyed tandemming) and it should be good for medium sized grocery shopping trips, with some alteration.
I've planned as far as simplifying the drive train to remove the rear cranks, assuming the rear derailleur could handle the weight of an extra long chain and attaching a beam rack to the captain's seat post as an additional rear rack.  Wasn't sure two more panniers warranted the extra length to be worth using though.
I'd kind of half thought up an alternative plan using a throw over pannier on the rear top tube but don't want to stress the tube in a direction it wasn't designed for/ bend it.

[Wowbagger]

I think it would handle badly.

I think Johnny Thin has some sort of extension to a mountain bike which might be more suitable.

[gordon taylor]

Someone did a world tour on a tandem with the back end adapted to take four panniers, IIRC. I'll try to find a photo or a link later.

[fruitcake]

I should have pointed out that this thread was inspired by a post in the classified section on using a redundant tandem for shopping duties.

Wowbagger,  I'm not particularly concerned about the handling, although I have ridden the bike stoker-less and I know exactly what you mean. 

I reckon the tandem stokerless handles better with cargo on the rear provided the cargo is as near to the centre as possible (in order to reduce frame flex), whereas a solo handles badly with 15kg on the rack and worse as the load increases. So, the usability of the tandem should increase as cargo mass increases despite the opposite being true with a solo. The need to get the weight central led me to the idea of a throw over pannier (to avoid the few inches of left-right displacement caused by the rack.)  I'm still working on: how to secure the throw over pannier as low as possible without stressing the rear top tube; how to use more of the space between the captain's saddle and the rear wheel. Brainstorming contributions welcome.

Another interesting benefit of luggage in front of the rear wheel is it will get shaken a bit less.

Gordy, tell me more.

[Phil]

I was going to bodge a rack together out of an old ironing board and weld it onto the seatstays and stoker handlebars.  I didn't do it in the end because it was a bit drastic, the bike would have weighed a ton, and I'd have had to replace the drivetrain as well.