if I understand correctly there is a problem with mixing fixed and percentage modifiers.
1: summ all positive fixed modifiers
2: apply percentage modifiers >1
3: add all negative fixed modifiers
4: apply percentage modifiers <1
would that work?
edit: or switch 3 and 4?
Well, the main thing I wanted was the Base Trade value to take negative numbers...
Though I realise research trade modifiers might affect it negatively, it honestly wouldn't bother me and work fine for my purposes; being that as you increase trade effectiveness, the negative trade 'upkeep' would rise as well (consider it a higher demand or whatever =P )
Basically, it comes down to me wanting to make upgradable capital ships using Starbase code, so they are technically starbases, but utilise the ability to jump between grav wells.
The issue though, is starbases don't use fleet supply, so the next best thing to limit their use is to make them drain the economy via 'negative trade values', thus if you field more than you can support, your economy tanks =P