"...while I layer on the torso..." I work off of block and skeletal models for a lot of stuff, drawing basic parts before heaping on the details.
It has servos in the spine, but I do need to run hydraulics and musculature which will give it a more normal figure when all's said and done. Otherwise there aren't any systems I would even think of placing in the abdomen; power and processing are in the chest cavity and the major sensors are crammed into the head. I thought about just running basic things along the spine for motile function, but the hydraulics at least would be anchored from the pelvis to the ribcage. Putting the main sets of myomer bundles along the belly rather than the spine would also make more sense from the perspective of leverage and all that.
Additionally, I'm thinking of cutting out the skeleton all together and going for a typical torso case depiction, leaving the internals for the imagination or a commissioned cutaway view.
