Wow, delurking after all this time...

In RTW, the "rebel chance" factor did NOT affect rebel spawn chances. It only affected the base 15 or 30% unrest for non-'owner' countries. The army lists from the file were used, but the spawn chance was elsewhere.

In RTW-BI, the devs added the rebel and pirate spawn values, in one of the campaign directory files (IIRC). You could increase that value to decrease the rebel spawning chance.
I had a quick look for that value in MTW but I couldn't find it (or remember exactly where it used to be in RTW-BI).

Anyway, I just wanted to de-lurk to prevent people repeating the goose chase that we tried in RTW! TEsting didn't reveal anything to affect rebel spawn chances (garrisons, forts, watchtowers, distance to capital, governors, etc.)

And while I'm delurked, thanks for the work on the shield bug testing and fixing Foz. There's no way in hell that I was going to manually edit that bad-boy EDU file!

Hey, because I'm feeling extra co-operative today, here's the way to alter rebels in RTW-BI:

"The easy way to lower the amount of rebels spawning is to open up descr_strat and find this line:
brigand_spawn_value 20
pirate_spawn_value 28
Raise the number to lower the amount of rebels, it's a denominator."