Thanks for the quick replies everyone!
Yes, the ideal would have been to establish a 400-ton lookalike class in advance, but as I said, I didn't do that, and the character is established as having a corsair; I want to use its deckplan, etc.
Say, what do people do when a player character rolls up a Corsair for their pirate? It kind of seems like such a difficult design to actually USE, as it's so unique. I mean, presumably there is a legitimate class of "light mercenary cruiser" that it was based on, but that will attract attention.
On the other hand, with 160 tons of cargo capacity on 400 tons, it does have enough cargo space to pass as a merchant: its cargo to tonnage ratio is about the same as a Type A free trader, and it might even make a profit given it's been paid off or stolen in the first place! Filling half of the tonnage with legit or low-cost speculative freight might actually be worthwhile; it can always jettison the stuff in space if it finds better loot while perhaps using the legit cargo cannisters and such as "cover." If it's been successful it can unload semi-sanitized "stolen" cargo into a warehouse at the port (assuming no customs inspection until it crosses the extrality line). Actually, one trick might be to take 80 tons of cargo (say) and use the rest of the big bay as a sort of onboard chop-shop to repaint, relabel and repackage loot as much as possible.
What's the best justification for the original ship design the corsair was based on? Unless it's Vargr, p. 129 of the Core Rules: "intended as a raider and pocket warship" - but that sounds a bit off - its lack of armor, streamlining and small craft seem to make it rather dubious for the warship or raiding role if it's likely to take any sort of fire, and it can't land and take off again on any world with an atmosphere. It does look like it could make a dandy "pocket mercenary cruiser" for a grav armor platoon: 20 troops and maint. techs in low passage and some officers in the staterooms, and use the cargo space to carry a platoon of grav tanks or g-carriers and their supporting scout vehicles, ammo and supplies...
I guess the best cover might be "we're a mercenary company en route between X and Y" - but a merc company is probably likely to attract more attention than you'd want from authorities - or would it, if it was "just passing through"?.
What it actually looks like is a 2G, Jump 2 merchant ship (160 tons of cargo on 400 tons is twice that of the free trader at 200 tons, and only 40 tons less than a Fat trader) for operations in frontier sectors well off any mains . . . that got 'souped up' with a bigger power plant and an extra 1G and some milspec sensors. (If only the standard design was streamlined!)
- I agree a corsair's drives can't be hidden to an internal inspection. Fortunately, fooling an internal search isn't an issue: in my Traveller universe the Imperium is a bit more into individual liberty: it doesn't let member worlds charge duties or engage in customs inspections on goods coming or going into a starport or highport (that's a violation of Imperial law). Similarly, IMTU, Imperial authorities only search inside a ship if they have very good reason to believe crimes against Imperial high are being committed there; random spot checks only exist in systems under military rule, a terrorist threat from the Ine Givar, etc.
- Instead, the customs inspect occurs when moving goods from starport to planet, and what the local customs patrol are watching for is small craft or ships that refuse to land at the starport. This can lead to some nice chases on worlds with small 'coast guard' level navies as a ship dives from orbit and tries to vanish into the ocean or pass low over territory to drop off a few grav trucks or boats full of smuggled goods before zipping back to orbit again, and local fighters or customs cutters try to intercept, but it's not what our pirate is doing...