Modified Dummy 13 90* Ball Joint

This is an extremely specific remix of the frame clavicle from this model that I needed for something crazy that I am making. Essentially I am attempting to use the 4-winged Ultrakill V1 model: (https://www.printables.com/model/901316-ultrakill-v1-dummy-13-wip) backpack AND wanted to also add a couple tentacle-ish things: (https://makerworld.com/en/models/574356?from=search#profileId-494671), but didn't see how I could layer the backpacks and still have it look okay. So I found the Dummy 4-arm remix: (https://www.printables.com/model/771749-dummy-13-4-arms-mod-upgrade-frame-and-new-armor-ch) and figured worst case I'll reprint the default frame, or the extra set of ball joints shouldn't look entirely out of place. This is an attempt (as of time of post untested ) to make a ball joint socket with a 90* rear ball so that I can still mount an extra set of "arms" (or tentacles) projecting backward from the main chest frame without having the “T” slot piece protruding and reducing the range of motion of the thicc arms that I am using…Without having to use my sucky lack of CAD skills, and exported to an STL in case anyone else may be able to use it. It is scaled at 100% to make the math easy if you're doing a 200%, 300%, etc. Dummy. If there is an issue with scaling let me know. Not a serious mod, just something super niche for a specific project. I will try and upload a photo of its use case once the project is completed. Don't hate me if I forget. Obviously adding a negative volume to the original part by @Incedius doesn't make it my own, so use this at your own discretion with respect to the actual designer please. Edit: okay, when I exported the STL from Prusaslicer it looks like it kept the scale at 50% because the part that I was working on was originally scaled to 200% size and I thought if I exported the STL it would naturally be 100% scale… sorry. Perhaps one day I'll fix that. I definitely find it ideal when models are uploaded at 100% so people can do with them what they want to rather than having to do math as someone with an art degree… so my bad there.