I have a rollaboard that fits inside my checked suitcase - the checked suitcase can then expand by several inches (unzip a zip)to hold the extra clothing / weight of the other bag. Presumably you have no weight / size issues once on assignment. The carry on bag itself expands - when expanded it isn't legal carry on size for any airline I know of, but it is very useful in a destination when I need to make a side trip by train etc. and don't want to lug my larger case with me (but a regular carry on size doesn't quite cut it). My bags are Delsey.