Child Objects

so i wanted to start out simple with child objects. something a little easy like... a roof for an amtrak NCPU. Easy enough. but how do I Get the scaling right?
https://railworksamerica.com/forum/
https://railworksamerica.com/forum/viewtopic.php?f=9&t=17172
GenericZack wrote:so i wanted to start out simple with child objects. something a little easy like... a roof for an amtrak NCPU. Easy enough. but how do I Get the scaling right?