Hopefully one with a solution to it this time

Is there a way to influence the modifier that controls manpower income reduction? My tuning pack has increased squad numbers. What I didn't think of in the planning phase was, that these numbers will automatically apply a heavy reduction on my manpower income, slowing down the whole game. I want to fix that. Without simply increasing manpower income overall in the army section.
For example: I start the round with a manpower income of +293. I order in a Grenadier Squad of 5 men, population cost 8. The manpower income will be reduced by 14, to +279. How is that number, the 14, the upkeep cost, controlled? How can I change it - so that there is less reduction/less upkeep cost.
I tried to find a pattern for how this works and I guess its a modifier, but I couldn't pinpoint the number and couldn't find any entries that might hint on the process.
This is literally the last thing standing in my way before I can release, so I really need to get this fixed. Any help is appreceated.