The January LURS meeting talk about the Q Stock restoration project is reported in the July Underground News, and mentions a CQ stock proposal from late 1962 to incorporate Q38 cars in CP stock trains. Presumably this would have avoided scrapping 25 year old Q38 cars when the older Q stock went, but modifications for compatibility to achieve another 15 years of service may have become uneconomic.
This was after the R stock programme had used most of the Q38 cars, and some had been put into COP trains. Another was used in this way in 1962 and a further 7 in 1964 for the District line. Perhaps only some 25 pairs of Q38 motor car and trailer would have remained. From my reading of the report, they may have been hidden in the middle of CP stock trains, so would only have made up another 8 x 6-car trains. This was not enough for the Edgware Road shuttle, but may have covered the East London Line 4-car trains, as was a later uncompleted plan to use 7x Q38 trains without costs of adapting to COP stock. I guess falling demand released trains and meant they could get by without the costs of modifying these older equipped trains.
I have read about it. It was called the segregation of flare sided stock. The aim was to convert the remaining Q stock to PCM equipment (originally it was hoped to be Metadyne but this was unreliable by the 1950s). A number of issues arose probably chiefly among them cost but also the design of the A stock which led to the freeing up of the O/P stock from the Met.
This was one of many plans floating around after the war.
Interestingly another parallel running scheme was to convert all the remaining L, M and N trailers to Q stock (which happened) and group together all the 1923-35 cars into 6 car formations with four motor cars and two trailers M-T-M+M-T-M. This would have required a fair few cars to be converted east to west but they could have been useful for operating the Putney service and other off peak services.