I based this concept on "
System Defense Boat Jump Shuttles" (T:S page 83) which described the combination as 700
dtons and said "Note that, when empty, the jump shuttle behaves as a ship of 300 tons (its actual hull size), which improves its sAccel, jump number, and fuel endurance." The "modular section" is actually a
separate hull which is detached from the drive section upon arrival thus reducing the ship's
mass by 2/3rds. How this would affect it's
volume I don't know but in RPK's "
GURPS Spaceships In Traveller" rules this isn't an issue.
Dalton “it's a Traveller vs GURPS thing” Spence