Any information or books would be helpful,
As mentioned, there isn't whole a lot to be added but here's something from Jerry Crandall who has done a lot of research on these last Dora variants:
- Oberkommando der Luftwaffe Generalquartiermeister reported that seventeen D-11 had been produced (four with EZ42 gyro gunsight).
- JV44's Platzschuztstaffel had at least one D-11 (Red 4).
- Some D-11s are reported to have been in the Unit Leaders School at Bad Wörishofen.
- There were plans to produce 820 D-11s at Focke Wulf's Sorau factory beginning on January '45.
- Fieseler's Kassel plant was to produce 1420 D-12s starting Jan '45.
- The plan was for the Arbeitsgruppe Roland to produce 1130 D-12s from May '45 on but the plan was cancelled in favor of the D-13.
Obviously these production plans were never realized.
Regarding D-13s:
Two D-13 protypes were built (V62 and V71) after prototype testing D-13/R11 was chosen as a production variant. The production was done by Arbeitsgruppe Roland, however the exact location of the final assembly of the D-13s is unclear (the Arbeitsgruppe consisted of several companies' plants on several locations) but it was most probably Mimetall Erfirt as A-9s and D-9s are known to have been built there. Arbeitsgruppe Roland was to be the only manufacturer of the D-13 with 1060 to be built starting Jan '45. The evidence regarding D-13 production is very rare. The only known evidence comes from Oberkommando der Luftwaffe Generalquartiermeister Nr.2766/45 document dated 7th April 1945. The document is reporting on the previous month (March '45). No later document is known to exist. There was a warning issued that there would be delays in D-13 deliveries due to the lack of documents supplied to the various factories and contractors. Based on the Yellow 10's W.Nr. 863017 would suggest that at least seventeen could have been built. The report mentions that two D-13s were in service by the date of the report.