Select parts using assemblies or manually selecting them in the
modeling window.
Upper body and Cabin floor are combined to form a watertight
cabin.
Outer part selection also depends on design iterations. For example,
if air dam changes between iterations, put it in outer parts rather
than upper body.
Save each group of parts in a separate .hm file. Create sets based on each
group.
For modeling efficiency, create a separate session for each
group.