I have meanwhile watched Yankee for a 2nd time, now in the subtitled italian version (could set a trend for me) instead of the german dub, which has it's usual shortcomings.
It's a good (6/10 I think), sometimes unusual SW, which belongs to the more interesting variations of the FoD formula. Brass tries hard to deliver several surprises by photography and montage to a not so surprising, but straight story.
But he doesn't succeed in creating an continuous overall style to carry the whole film, there are also some unimaginative shots which have a purely routine look (like the sequence with the rafts). Routine are also many of the costumes which have only a "50s american middle of the road western" look, typical for most of the early SWs up to 67.
Another major fault are imo the two leads. Leroy, who looks like an unhappy salesman beneath his much too great hat, lacks the necessary charisma to fill in his role (which would have been a great one for e.g. Robert Woods) and his dialogues.
Adolfo Celi has done better (Thunderball), here he gives us too much of the usual fierce grinning mexican heavy, and he has the burden of a slightly ridiculous looking (and much too clean) costume.
The overall impact is nonetheless positive, because there are so many interesting ideas concerning dialogues, shootouts, violence, story development, which is all done in good and inventive SW fashion.
I would like to see a director's cut of Yankee.