For the guard, made the base of the guard using measurements from all three of my sources. The sketch of it is shown in Photo1. Extrude the design by 2.83cm. It should now look like Photo2.
Now, onto the design of the guard engraving. You can either measure the guard engravings by printing the Cardboard Youtuber’s template (in his Youtube video’s description, the sword template is already to scale) and create the sketch using such measurements, or decal the engraving and trace the engravings. Both sides have the same engravings is symmetrical, so you can just do one half and just mirror it onto the left side, then mirror it to the other side of the guard, shown in Photo3. There is also a center part of the engraving, measurements are shown in Photo3.
Note: the obtuse angle should be around 119 degrees.
After you extrude the engravings, the guard should look like Photo4.
After, extrude a 1.27cm diameter hole (just like in Step2) through the middle of guard. After, shell the guard by 0.7cm. Make a 0.5cm thickness circular extrusion around the 1.27 diameter (to allow the dowel to stay in place, like in Photo5). After, split the guard into two halves for easier assembly and 3D printing.
Optional: Make lego-like holes that connect with each other. While I ultimately found that they did not do much to help the piece stay together (the infill was not thick enough and therefore the extruded cylinders were too fragile and broke, I used a 15% infill but you should use a higher percentage infill like 25%), it can help when attempting to super glue the parts so they won’t be misaligned.
The STL Files are found below.