I have a problem with the parts shown in the attached photo, and also a general design concern about the full project (Evangelion Lance Of Longinus).

  
The problem:  
I split the model in two and added connectors, but the STL file containing the female parts and their connectors wasn't saved. Is there a way to recreate the connectors cavities with mathematical precision (i'd like to avoid placing the objects manually with move).

  
the design concern:  
The sections as designed by the original creator, aren't completely hollow from end to end. I assume that's intentional to insert short metal rods inside, not as long as the full staff (2.4m), but to connect each adjacent segment.  
However this brings some issues:  
\- when i will glue the parts, i might not have the single inner rod as a precise alignment support;  
\- neither end is fully hollow, and bambu studio generates supports from the base up to the end of the cavity. it's very difficult to remove the support in such deep cavity and inserting the rods with some spare cms of supports might be tricky or incorrect.  
Would it be a good idea to completely drill through the parts and then freely insert my available rods of varying lengths, or would you recommend for example a proper technique/tool to correctly remove the supports stuck at the end of the cavity, or even generating different support in bambu studio. 

thanks to everyone who will reply!!

Help with sliced pieces and connectors/Design concern regarding metal rods