Merge Two Foil STLs Seamlessly

I have two STL files of a mechanical foil profile that were originally split only to fit a smaller build plate. I now need them combined into one uninterrupted, watertight body while preserving every millimeter of the original geometry. All dimensions and tight tolerances must stay exactly as they are, so any blend between the two halves has to be perfectly smooth with no change to the air-foil contour.

Here’s what I’m after:
• Stitch both parts together, eliminate the split line, and return a continuous surface that will pass all mesh-integrity checks (no self-intersections, non-manifold edges, or holes).
• Maintain the existing reference dimensions; target deviation should be under 0.05 mm across the joint when compared to the source files.
• Supply the final, print-ready STL plus the editable CAD file from whatever software you work in—SolidWorks, Fusion 360, or an equivalent high-precision tool.
- Remove cavities from the top and lower foils used to attache the two pieces together.
- Create cavities for attaching the foil to the skid.
- Add additional screw holes (4 on each skid and elongated foil)) to attache the foil to the skid.

I’ll run a section-by-section overlay in my own QA, so please keep the final model clean and well-layered for inspection. If anything in the original files looks inconsistent, flag it before you proceed so we can agree on the fix.

Turnaround is flexible but sooner is better. Let me know if you need any other data from me and what software you plan to use, and we can get started right away.