Although efforts were made to match the augmentation trailer with the rest of the unit this didn't always work out in practice and a lot of making-do and mending was done after the war when the backlog of maintenance and war damage repairs often became critical.

Once the nucleus of electric stock had been established the Southern threw itself into the wholesale conversion of its suburban coaching stock into electric units. As each extension was made to the system stock was introduced which had been converted from that made redundant by the previous extension. The principle was to take whatever the existing configuration had been and rebuild it onto standard steel underframes with the long term view of retaining the underframe and eventually replacing the bodies.

The exception to this arrangement mainly concerned Ex-Brighton stock. The most modern coaches from the LBSCR were referred to as "Balloon Stock" because of their unusually large size. Unfortunately they exceeded the loading gauge of the erstwhile SECR and LSWR and despite their comparative youth they ended up in the scrap yard.

The stock converted from the ex-LBSCR CP and CW stock, moreover, was already mounted on steel underframes but these were non-standard in terms of the general policy.

This stock was converted to DC operation, formed into three car units, upgraded with heaters and communication cords and fitted with Southern style driving cabs in 1928 - 29. They were, however, easily distinguished by the segmental roof profile as opposed to the almost square section of the ex-LSWR and ex-SECR stock. The impression was that the roof line was lower than the others although in reality there was very little difference.