Patrick,
Fomapan 400 is my standard film, and I agree, most advice is someone else's opinion, and I follow my own instincts, the 400 is, I think, a wonderful film, and I like rodinal for most films, and have done so for many years,I have tried other developers, including D76/ID11, but always come back to Rodinal because I love the tonality I get with this combination that I can't get with anything else, also I find any film appears sharper due to the edge effect you get with Rodinal, also, F400 in 35mm has no anti halation layer, which can give some very nice effects in the right light, but the 120 has a good AH layer,this is the green color that the developer is after developing the film, and I use more 120 than 35mm, I love the stuff, my favorite film,
Richard