Cepheus is sort of like rules light mongoose, though I really do not know the current iteration of mongoose that well. A player in the one game brought in the playtest docs he had printed out, and we looked it over before game, and I passed. At that time I was priming for a M-Space (Basic Role Playing like CoC/RQ) that I ran with my setting also. It could probably mechanically work with my setting, though I don't really know what assumptions are baked in.Creating starships is one thing I have not really ventured into. Typically, my games have been in the Spinward Marches or Trojan Reach where the ships are usually traders and cutters and nothing too militaristic.
I did grab the Cephus package for Foundry and switching it up to run Traveller (pretty easy). Im still trying to get the hang of Foundry, I've been running just discord and using excel files for my PoD game.
What differences does Cephus make, and do you like it better than Mongoose?
There used to be a bigger guild of us spacecraft builders, up until about 5 years ago. I like the simpler rules sets, not to have to use a spreadsheet, and to make deck plans. I posted some over on reddit and Citizens of the Imperium, the official Traveller website. I am heavily influenced by the Terran Trade Authority books, last ship the players had was from there.