Was literally just thinking of starting a similar thread.... Have been using Tun... It's ok. Is Sothis to Ceos better though? Using the ol Python since it can go anywhere more or less.
You can run a BUNCH of data delivery missions between Ceos and Sothis but there is only a single FED faction there so, many of your missions will be for factions that are not federation aligned unless you want to spend a lot of time logging. I find that I make a boatload of credit by cherry-picking long-range cargo delivery missions (trying to get a bunch to the same station or system) while running data back-and-forth, then running the deliveries back to the bubble.
Haller City @ Barnard's Star has 4 or 5 FED factions. Harder to get allied (more factions to satisfy) but more FED missions, many of them to the same systems and stations, even from differing factions. I am even running cargoes simultaneously for factions that are at war with each other. I regularly fill my cargo hold with 360+ ton cargo and data delivery missions to 3 stations in the Ep Indi system (1 jump), one of the stations is Mansfield so I pick up as much "Indi Bourbon" as they will sell me each lap and I am increasing rank in all factions as I go round and round. There were donations missions but when I hit Lieutenant a couple of days ago they dried up for me. Lots more "steal this" and "massacre that" missions now. Anyone should be able to get the same results, at least up to the point that I have, I switch back and forth between this and Ceos/Sothis, running rares on the way out so I am not dead-heading earns a million or so more and raises REP. In addition, these cargo delivery missions also drop various, rare engineer materials in your inventory, stuff I keep seeing other users complaining about how difficult they are to procure. I wish there was a way for me to sell all these exquisite focus crystals and modular terminals and micro-weave cooling hoses, oh my!
I tried Ceos/Sothis/Bubble in a Python but for me, just not enough legs and not enough tonnage, was taking 38-40 jumps to make the bubble deliveries, the Anaconda can hold (stripped) well over 400 tons and still jump (w/level 2 FSD mod) well over 20 LY laden making it more like 26-28 jumps to the bubble. HUGE difference in time & effort plus: 10-15 million credits per lap in a Python vs. 30-60 million (depending on mission stacks) in the Anaconda. Also, in a Python as soon as you start accumulating those engineer mats your cargo cap takes a HUGE hit, bad enough even in the Anaconda that I keep throwing the stuffs over the side or selling them at the CM. In my completely A-rated Annie I can carry a little over 360 tons cargo and earn roughly 40-50 million per lap.