I recently started playing the one row melodeon, a Hohner 1040 "Vienna", with four bass/chord buttons. I've been really enjoying it and I've found the layout very intuitive as I play the harmonica too. Melodeon.net has also been a great source of information.
On the bass side of the one row melodeon the IV chord is available on both push and pull. I find that IV chord very useful because in the music I've been playing (German folk tunes) the IV chord is used to accompany I, II, III, IV or VI melody notes, which are a mix of push and pull.
I've now also acquired a three row GCF Hohner Panther which are plentiful here in Texas. I'm still getting to grips with the layout, but my understanding is that the home row is the middle one in C meaning a IV chord of F major. However, on the bass side F major is only available on the push. When playing a melody in C major, is the solution for notes which need the F chord as accompaniment to play them on the push on the G or F rows?
Put differently, if I look at the bass side the only chords available on both the push and pull are Bb and C, the IV chords of F major and G major. Does this mean that I can play tunes in F or G major using the same fingering as on my one row for the melody and using the F, Bb, C or G, C, D basses? But if I want to play a melody in C major it's better to learn different "all push" fingering because of the absence of an F chord on the pull?