you can only allow the projectile to be scaled in hte same way as the modell is scaled. other way is to deactivate the projectilescaling, that means it returns to it's normal size. i don't know how to scale projectiles without scaling the unit too
to the building art: what exactly do you mean? the buttons for upgrading? the animation? the modell? please a little more pecified...
You can't change the upgrading art of an building being built or upgraded. When a building such as a Blacksmith is being built that art cannot be changed as is the same when being upgraded.