I got burned on some dead Ash and some soft Maple last season that I split too big, like 6", but I'm feeding cat stoves. Your tube stove may not be quite as picky and you have a longer drying season. I don't think you have to go
real small, maybe 4" max dimension, which I'd call medium. Your stack pics look about the right size. 4" is what I'm holding it to this season, feeding all cat stoves. I'm stacking a bit late on some dead Ash and live Silver Maple, but I have a buffer with the dry, little stuff I got for my SILs, and I've got a windier spot where I'm stacking the Ash and Maple they'll need later in the season...I
should be OK.