Hmm I am not exactly sure as to how you go about doing this, the targets your looking for will either be planet bonuses or the planet data itself... My only concern with editing the planet bonuses with this new one (and making it's occurence chance 100% like your saying) is that it would shove out all other planetary bonuses. But again, I am not totally sure that that will even be a problem.
Maybe if you try entering some code into the planet bonus data like this:
floatBonus:ShipMaxSlots 5.000000
Other than that, not sure what else to say, hope it helps 
