Train formations (1959 & 1972MkI stock) on the Northern Line

Both 7 cars.

1959 stock was DM-T-NDM-DM+DM-T-DM

1972 stock was the same, except one of the middle DM's was an UNDM.

With he proposed link to Battersea, would the Kennington loop become redundant, or at the very least for emergency turns only?

Thus saith carto metro

Let me throw a curler-what if instead of extending the Northern Line to Battersea, some bean counter at Tfl decides a cheaper option would be to extend the Victoria Line from Victoria, straight to Battersea?

Yes they were, and yes it was - which is why the 1972 stock were double-ended: so that any 3 car could be coupled to any 4-car

Numbering:
The first two 1956 stock trains were numbered from A end to D end as follows - the rest of the 1956, 1959 and 1962 stock followed on in sequence:
1000, 2000, 9001, 1001 + 1002, 2002, 1003.

1004, 2004, 9005, 1005 + 1006, 2006, 1007

So A end DMs were even numbers from 1000, D end DMs ( driving motors - i.e a car with powered axles and a driving cab) were odd numbers from 1001, trailers were even numbers from 2000, and NDMs (non-driving motors: in the four car units only), alternate odd numbers from 9001 and all odd numbers from 9401 (i.e for the 1962 stock).

1962 stock was all four car, 1956 and 1959 stock was equal numbers of three and four car. The individual units were fixed, but any two units could work together.

1972 stock (both marks):
32xx-42xx-43xx-33xx + 34xx-45xx-35xx

3xxx cars are motored and 4xxx are trailers. The motor types are all different. The 34xx UNDMs (uncoupling non-driving motor) have no driving cab, and they are always in the middle of a train. The 35xx DMs have emergency couplings only, as they are always on the end of a train. The 32xx and 33xx DMs have both cabs and autocouplers, so that, whichever way round it is, the 34xx car of a 3-car could always be coupled to one or other end of a 4-car unit. However, unlike the Northern Line, there is no way a Bakerloo train can be turned round in normal service, so the 33xx cabs are now always in the middle and have not been equipped with the more recent upgrades - and indeed in one unit the 33xx car has been replaced by an NDM (ex-34xx).

When I used them the guard was in the rear car.

Or the 33xx car, depending which way round the 4 car set was. Always the leading end of the last car - the traditional place for the guard on all LER/LT trains.

The Met, always different, had them in the rear cab up till and including the O stock, but the P stock had it in the saloon so that eight-car O/P formations could be made up with a P stock car at the rear to ensure the guard was adjacent the platform. The A stock also had it fitted in the standard LT position and had to be moved to the driver's cab when converted for OPO. Similar conversion work had to be done on the 1972 mk 2 stock.

From the C stock and 1973 stock onwards, the guard's controls were in the cab, in anticipation of conversion to OPO.

The only other exception I know of was the "special" NDMs on the Northern Line for the 9-car scheme. These allowed the guard to ride in the seventh car, ensuring he would be on the platform even at those statoins where the rear two cars stopped in the tunnel.

That's correct. The reversible 4 car units could be coupled to the UNDM from either end - ie the 32xx or the 33xx.

I have often wondered if an 8 car train could have been formed 32xx-42xx-43xx-33xx+32xx-42xx-43xx-33xx

Or could a 6 car train been formed?

35xx-45xx-34xx+34xx-45xx-35xx