There isn't really any ambiguity about weight.
A volume large enough for 5 people with heavier materials would likely create greater dry dock logistics and cost challenges, everything else being equal.
And the heavier the vessel, the greater the power requirements, greater power = more batteries = even heavier.
The DeepFlight Challenger had a carbon fiber composite hull, was designed by an expert, and was constructed before the Titan.
Carbon fiber (CF) composites have been around for a really long time.
I vaguely remember observing testing of prototype CF CAT scanner beds way back in 1980 or so.
I cannot remember the weight specs.
A lot has been learned and tried since then.
Perhaps of interest:
https://www.compositesworld.com/articles/the-first-composite-fuselage-section-for-the-first-composite-commercial-jet