Yes, most films doesn't really have their respective box speed. With most 400 film I start my estimations at 250. This is especially true for the eastern Europe films. (The now dead Forte/Adox/Bergger 400 film was even worse at around 200. But other aspects of it in larger formats made it a lovely film.) Now, Foma isn't Forte, but they do relate in the sense of both factories using quite old technology and machines, so 200-250 sounds like good advice.
The "Expose for the shadows and develop for the highlights" (to shorten what jtzordon said) is something which teachers at every darkroom class have repeated for the last decade or so. Hmm, there must be some truth in that...
Anyhow, the "recommended" developing times is in some data sheets printed as "recommended starting times", so you should be prepared to adjust the time (and nothing but the time) until you are satisfied with the results.
In this particular case your weather is like my weather. I.e. dark for almost 18 hours and a dull wet grey in between. That is one end of how a scene is lit, i.e. very evenly. The other end is direct harsh sunlight. Now, the "recommended starting times" are set to be in the middle of these two "extremes". Those of us who shoot Large Format sheet film or possibly Medium Format (usually 12 exposures per roll of film) are more accustomed to adjusting the developing time according to the light situation in the scene(s) we shoot. Without going into the particularities of it, I personally use one of 3 developing times for any film/developer combination. One for dull weather, one for bright light weather and the third one which is in between and rather close to that recommended starting time.
In short:
Dull weather: +25% developing time
Somewhat overcast: normal dev. time
Sunlit scenes: -20% dev time.
(The ISO setting doesn't differ much even though the developing time does. Using 200 at sunlit, 250 for normal and maybe even 320 for dull would be my personal starting points.
To come back to your shots of that turbo charged dog
, they are taken in dull weather, so you should adjust the development with some extra 20-25%. I recon that will give you about the boost you want.
Neither me nor anyone else would want to send you into a long lasting testing cycle. So, these tips are my "shortcuts" to you. Even though these values may differ somewhat from person to person, following the above tips should get you quite close to a very good result.
Finally, you don't say if you intend to have the negatives printed "traditionally" in a darkroom or if you scan and print them digitally (i.e. "hybrid"). For the latter, it's important that you don't overdevelop.
//Björn