[Spike]

Great find, Dave. Just posted a blog comment hypothesizing this sheet layout for the "red ink" sets.

Red Backs (unknown number of 20-card vertical rows) at "left" followed by 11 Connie Mack + 9 Teams (in 10-card vertical rows)

Topps might've never intended to cover more Teams than needed to fill the sheet, given their focus on Red Backs + Connie Mack as a "unit." It also means including Ty Cobb in the Connie Mack set would've taken away a Teams card to stay at an even 20 total cards (2 side-by-side rows).

With that layout, reversing a sheet between front and back printing yields the Red Back front / Teams back you snagged. It also implies Teams would've been on the far right edge, with your 7-12 Red Backs panel on the far left before being swapped. A common sheet could also explain why Connie Mack cards with rounded corners might exist.

Sometime after the first two printings, probably after Red Backs proved a hit and the "1950" Teams cards didn't solve the legal problems with Bowman, Connie Mack and the Teams were printed on separate tan stock sheets, explaining why no Red Backs appear on tan. (You already posted a mis-cut showing Connie Macks and Teams side-by-side on the same sheet, which would happen for all 3 printings.)

What do you think, does this layout hold water?