I develop at 1/50 for Fomapan 400, develop for 12 to 14 minutes for 120 depending on light, for sunny days I develop for 12 minutes, if very dull I would give the extra 2 minutes, for 35mm I develop for 12 minutes whatever the light, My main reason for using 400 is that a lot of my photography is in very low light sometimes down to 1/2 second at 4, and I hand hold, hence my love of rangefinders, especialy the old German ones with leaf shutters, however, this week, just for fun, I used Fomapan 400 at 200 and 400, that is I took one at 400 and one at 200 of the same subject, and TBH the difference is very slight, the 200 is very slightly heavier, but the results are the same, I have just been ptinting them and there is perhaps 1/2 grade difference between 200 and 400, I printed straight, no dodging or burning, and certainly for me my 200 negatives are not thin, slightly heavier than the 400, but they each print just as well, no blocking up no problems at all, so I will continue to use box speed as I have always done, It might not suit everybody but it suits me, I have been using the same combination of Rodinal and Fomapan 400 at box in Rodinal for 15/20 years, I have tried it in D76, stock for 8 minutes again at box speed and again very nice negatives easy to print, but I personally think that Rodinal adds something to the Fomapan both 200 and 400, I have never tried Xtol, for most of my Photographic life I have used Rodinal and I guess after so much use I know it well, and prefer it to anything else, whether it be Kodak, Ilford or Foma