Impossible to create Historical League with only 10 teams?

[Max Boyer]

Hello everyone! My name is Max and I'm new to this game.
I've spent several hours trying a MULTIPLAYER CUSTOM ROSTER FILE LEAGUE using the HISTORICAL DB that's in-game without any success.
It won't load when I click "OK/Confirm (green button)".

The only time that it let me use the Historical Players is if I am using the HISTORICAL ROSTER FILE, but I cannot adjust (lower) the amount of teams by doing so. Even during the off-season, I can only Expand the league, not reduce it.

What I want?
I need a league that would start in 1990-91 Season and would have 10 Teams using the Historical DB with the Real Rookies as we move forward.

I've read that I would have to create a DB. Should I start in 90-91, export the DB and edit the file and create a new ROSTER FILE?

I've search the forum A LOT. I have lots of experience in this field but I have little to no knowledge when it comes to create a DB like that.
Note: I've gained a bit of experience after finding and using SQLite Studio and I was able to modify a few things about my game. Great tool, but I still need help understanding "how to" assemble a custom database.

This is a great product. I love my experience so far with the game. Thanks!

NOTE: I now have the ability to import the players from another database into mine without having the game crashing (really simple) but would still appreciate if there is another way possible down the line.