We use a traditional formation, except that, being a large band, the euphoniums have a row of their own in front of the baritones, and we have two rows of horns. We still have the flugel in his old place, between the sop and 1st cornets, which is a pity as I think it is much better if he's with the horns, preferably the opposite side to the solo cornets to make the most of the spacial separation when they are bouncing off each other.
I remember going to see Grimethorpe in Birmingham under Elgar Howarth (c1977) and they used 3 or 4 formations at different points in the concert to suit the music being played. When Bourgeois' "Concerto No 1" was used at the Nationals quite a few bands sat the sop on the front row, as he had written the "top cornet" as he saw it as the lead player.
I've also come across bands where the top trombone has sat in the middle of the section (Melbourne Staff Band did this on their last visit to UK), and the Illinois Brass Band at the Open this year sat the Solo Euph next to the 1st baritone rather than on the end.
I'd like to pose a question to the other bass players on the forum: we are due to reorganise our section shortly, and I should like to see 1st Eb and 1st Bb sitting next to each other in the middle, which is not the way it has generally been done in our band. What do other bands do about this?