In the GC3 ship designer module, the total available mass for components, was displayed for a given ship. You could try adding attack, defense, or other modules, until you went over the available mass limit. You could tell by mousing over each component, if it would fit on the current build.
In the GC4 ship designer module, I do not see an indication of the total available mass for components, and a rating for each available component as to its mass.
I can just blindly click on a component to attempt to add it to the selected ship, until I get a message that the selected part is too heavy for the current ship design, and that I must remove another part.
What am I missing, or has the ship and component mass concept, not yet been added to GC4?