Unfortunately doing it that way only adds to whatever stat to the ship while it is in the hanger, once it is put into a fleet it loses the bonus. Probably requires a different approach then, assuming it is possible in the first place.

Hm, if I toss together how racial modifiers modify ships (keyword "/ClassShip", example 

path="ClassEmpire/ClassColonizedStarSystem/ClassGarrison/ClassShip"), and how system improvements modify ships (see above), my next attempt would be something in along the lines of

<Modifier TargetProperty="Damage" Operation="Percent" Value="0.25"  Path="./ColonizedStarSystemStateColony,ClassColonizedStarSystem/ClassGarrison/ClassShip"/>

Can't check it at the moment but would that work?

No, still causes the ships to only gain the bonus damage while it is in the hanger and not when added to a fleet.

I am thinking I might have forward the property to ClassColonizedStarsystem to get things to work the way I want them to, not sure on that though.

The issue here is not the path, but that the modifier applied by those XP on construction improvements is unique: ExperienceAtShipCreation. The bad news is that as far as I can tell from a search, this is handled by code and not in the xmls; MonAmiral could confirm.

MonAmiral wrote:

Hey folks,

This would have to be implemented in code and isn't possible with a mod. Sorry!

Okay, thanks for the confirmation on that. Was not sure if there was anything that had been implemented other than granting experience at ship creation to hook into.