Well, in fact data was extracted automatically by Tafoid (by using a script to run all the games one by one and by using a modified MESS which output the SRAM size).
My part of the job was parsing the results (and megadrive ones) and translating them into the xml. Pretty boring stuff, but imho it was useful for the project: the main advantage in using the xml for SRAM instead of the header only, is that through the <dataarea> approach we can later also add preset SRAM for the bunch of games (Ken Griffey?) which needs it and default the other games to anything we want (0x00, 0xff, 0x35 or whatever).
The code to support this is not present yet, but at least the basic infrastructure is there
Anyway, back to the case of SRAM size mismatching the header value, please add a comment in the xml for the carts which present this issue. They could be worth further tests to see if any has a wrong header