You can fit a tier 1 Outpost entirely in a Fleet Carrier as long as you don't have too many services installed. I have "Refuel, Rearm. and Repair" services up and running and it uses 930 T of the 25,000 T capacity - so 24,070 T left for storage/transport. An outpost only requires 18,473 T of materials. So yeah, you can easily fit it. I've completed 2 Outposts and 1 Industrial Port (36,829 T) before the tick this morning. I'm working on a Tier 2 asteroid base now (53,723 T). In fact my FC is fully loaded and now I'm waiting for FDEV to re-enable the colonization building process so I can start unloading her...
So, yeah, a Fleet Carrier is extremely beneficial to getting things acquired and moved.
That being said, a lot of the smaller tonnage items are pretty easy to find so I just pick them up with my Cutter (760 T) in nearby systems. The real payoff with the FC is when you can park it right near a source which requires the most aggregate tonnage (a Surface Refinery). Then just load her up with what is effectively the majority of the required materials from a single place.
Everything you transport with an FC will require both a loading round trip and then an unloading round trip for each load. If you simply use a large ship for transport its only one round trip for each load but your gonna spend a lot of time jumping around between systems. So, the FC requires twice the flight cycles but if you use it effectively you don't have to do any intersystem jumping with the ship you use for loading/unloading the FC. (I also use my Cutter (760 T) for loading/unloading the FC)
Another notable consideration is that "CMM Composites" are only obtained from SURFACE refineries. (The other Refinery commodities are not so limited). So, if you plan on parking your FC near one for ALL your Refinery commodities (which is a good idea), you are going to get very good at planetary landings!
I'll get all the "lower tonnage" Agriculture, High-Tech, and Industrial commodities by just flying to nearby systems in my Cutter. For the the Refinery commodities, I'll park my FC nearby my source and load up. Then there is "Insulating Membrane" which is also kinda restricted in its location/availability so I'll use a medium size ship (T8) with a good jump range (41LY) to go chase down the relatively small amount required in a single trip (Its also a Refinery commodity but fairly restricted by location).
Get a Fleet Carrier. Its a game changer. Especially now with colonization. Check out the "Pilots Trading Network" (PTN) if you want to streamline your quest for a Fleet Carrier. You can actually earn enough credits in only a couple of days to fully pay for an FC if you have a large capacity transport ship to work with and about 1BN credits to bankroll your initial investment (trade purchases). An FC costs 5BN, but you also have to consider the weekly upkeep (9.5M for Rearm, Refuel, Repair services). You'll also want to have a rebuy in the bank for your largest ship (just in case). Most folks suggest at least 7BN in the bank before pulling the trigger on an FC. Check out the PTN discord for specific details.
