Nice cards Kevin!, the 1888 Minneapolis cards are a bit easier to collect than the other 1888 Western Association teams with most of the players/poses being Fa cards.
Regarding Western Association cabinets, we do know that in general the 1889 cabinets are more common than 1888 which would suggest the most difficult WA teams would be Chicago Maroons, Kansas City Blues, and St. Louis Whites (these three would not make it to 1889). Of these three teams, St. Louis Whites was the first to disband (June 20th of 1888) which likely led to extremely few cabinets being ordered. The new for 1889 teams (Sioux City, Denver, & St Joseph) may follow with the teams that played both years being more likely to surface.
I just caught your last comment on the Nicholson . . . the Nicholson I used as an Fb example might be from your collection (or Burdick, LOC, etc.). That Fa/Fb/Fc composite is from ten years ago when we were gathering lots of images for the book. I will re-create Fa vs Fb vs Fc from my collection (all Detroit)