[quote=@BCTheEntity]
[@Necroes] It's worth noting that the "Chaos cultist looking guy" doesn't actually look that much like a Chaos cultist. I'm also not sure how somebody in Vespin's position knows so much about Chaos, considering how stringent the Imperium is on killing most who learn about that sort of thing, whether or not they're officers.
[/quote]

I second that.
Knowing an awful lot about the alpha legion.

Anyway.
I'm not saying that if there was a cadian armoured company on this ship, there wouldn't be tanks.
I'm saying this ship is too small to transport a tank company, or any notable amount of troops.

Sure, evidently there has been some guard troops attached as extra security. Probably since the sloop was expected to go into combat, so they made sure some extra men were given to this ship.
However, seeing as this is a weedy and unimportant ship, it mostly had to make do with abhumans. Ie ratlings.
Which the ship hasn't complained all too much about, after all, more nice food is always nice.

It's up to JB, but this size of ship wouldn't fit any tank groups at all. It would barely fit transporting troops at all.
It can have some extra guys, a couple of dozen of guardsmen from f'ex cadia stationed here to beef up the security. But any large amount of troops would not fit on the ship, since it lacks a lot of compartments.

From a wiki.
"Given its specialist role, the Viper is unsurprisingly limited in many ways. It is a tiny starship, with very restricted space for additional components. Furthermore, it is not heavily armed, as extensive weapon batteries would draw vital power from the sensor arrays and engines. They are rare vessels in the Calixis Sector and are not ideal vessels for Rogue Traders, given their highly specialised nature. However, more enterprising and wealthy Rogue Trader dynasties will often employ a Viper as part of a larger fleet, leapfrogging ahead of the main force to rapidly establish the nature of each planetary system encountered."

Restricted space for additional components. IE cargo space.

Anyway, i'd say it's up to Gm. After all i don't recall being told what is on the vessel in terms of troops, which is fair since we're going in not knowing what is on the vessel.
So why should we know what is on the vessel.
Although, the ratling being from ship will know what is on the vessel, so JB should have told you necroes.

Anyway, i'm hacking some ship systems.
Lalala, beep beep boop, i'm helping and not knowing what is going on in the armoury :D