Mesh Bot Solid Conversion

I have an OBJ file of a small, stylised “bot” that I want rebuilt as a true, watertight solid so I can edit every feature comfortably inside Fusion 360. Please do not rely on the automatic “Convert to Solid” command; I need a clean, fully-parametric body with properly aligned, tangent faces and continuous, smooth curves. Overall height, width and length must remain identical to the original mesh, but I do want one deliberate change: enlarge the tail opening so it matches a USB-C (C-type) charging profile and add a simple snap-fit lip, as shown in the reference image, to let all printed parts clip together firmly.

When you are finished I expect:
• a native Fusion 360 design file (.f3d) or a STEP that opens flawlessly in Fusion with a full feature timeline
• clean, single-body geometry that passes Fusion’s “Check” and “Section Analysis” tools with no gaps or self-intersections
• the modified tail hole and snap-fit detail ready for 3-D printing without extra support work on my end

If anything is unclear, let me know before starting so we can lock down the critical dimensions. Once we agree, I’ll send the OBJ and the reference image for the tail feature.