If so, then won't that make it all but impossible to build a ring/sphere world? (Don't you have to build them in place, using non-orbiting spaceyards, since the components are too big to transport from a planetary shipyard?)
Add a Barge, that is 2040 kilotons. It can carry 1 engine, a Bridge, LS and CQ, and one of the Ringworld comps.

Solves that problem nicely.