I've been reading all of the tutorial documentation when it comes to modding, but I'm still confused. So if I want to create a custom sized sprite body, what offsets am I determining? The outer edge of the shape for the hitbox?

And I have another question, to create a flying unit, like the one found in the Trappers mod. I need to use Lua scripts right?

And one last question, how do I add sprite details to my sprite when its damaged? I've seen my troops lose limbs and leak blood, I've seen part- was all of that an optical illusion? I'm so confused.

Any help appreciated. Is there like a super huge guide for ultra noobs out there? You see I want to add a pegasus unit with a crazy machine gunner on top. And I can get the parts done, but I'm confused. Although the wings don't move because I can't figure that part out.....

The sprite's hitbox is determined by the game based on its shape, you don't need to worry about that. you can however use the 'Depth' variable under the AtomGroup to move the collision outline back or forward, which is largely unnecessary in most cases. When determining offsets, there are a few.
SpriteOffset determines the center of gravity for a sprite, from the bottom-left corner. Usually it's easiest to just use half the sprite's width and height for the X and Y values. From there you've got offsets such as MuzzleOffset, JointOffset, SupportOffset, and a bunch of others. These all have different applications, such as JointOffset, which determines where the sprite will attach to its parent.

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For flying units - minus dropships, yes, you'll need a Lua script.

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When a particle that has enough force / sharpness penetrates a movable object, a predefined 'wound' will appear at the entry - and if it's sharp enough to penetrate all the way through, exit - points. These wounds all have the same sprite (unless you randomise it with a script), and can be changed under the "EntryWound", "BreakWound", and "ExitWound" fields. Entry for the wound entrance, exit for the exit, and break for loss of limb or attachables, at the limb's joint.

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As for a guide - I'm afraid not. There's this page, though, which might answer some of your queries. Always feel free to ask for help though, people are quite friendly here.

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As for your idea, horses in CC are pretty difficult to do, especially with a mounted rider on top. And then flying, at that. You'll need someone with proficient Lua skills to script the animations, movement, and mounted rider, unless you're not opposed to using hacky workarounds. We should totally have an AHorse class

Ah yeah, i'm already looking at that page. As for the mounted rider, all I'm basically doing is making the unit flying and making its legs the horses legs, and making its arms the riders arms. The wings wont be able to move for obvious reasons.

I couldn't figure out how to attain a copy of B27 or I'd try the Trapper mod myself sadly. Do you know where I could find a copy? no torrents show up anywhere.

As for lua, I would rather learn all that myself.

One thing I wonder though, Could I use lua script to add maybe... CAPES to my Actors?

You could have an incredibly complex script to animate separate segments of a cape, but you're best off using a static attachable, with animation if you're up for it.

The unfortunate thing with AHumans is that they've only got two legs :S
If you were to make it an ACrab, you could have the turret look like the arms, and the head either in the sprite, pinned as an attachable, or held in place with Lua, allowing it to rotate. Whatever's best for you, though.

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There's a hotfix for Trappers here, though I've not tested it.

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For wings, you could have them as scripted attachables, using a Lua script to run through the frames as it's in the air. You'll have to sprite each frame of the wing folding/unfolding manually, however.

Oh thanks man! I don't know how I missed that.