I haven't read ac 43-13 1b ,..I'm just curious if there is something that brings that attention to the fuselage,..I'd be willing to repair a section with in the fuselage with a splice and an internal or external sleeve,.and feel all warm and fuzzy about it,..the fuselage is a conglomerant of several structural sections,..
And don't take this wrong ,..I'm speaking personally here,..the strut and my knowing the stress's it is exposed to,..I would weld any crack or break close to the ends of a strut,..because vibration is buffered by the connection points of the strut ..which are on each end ,.and the repair would not be exposed to severe vibration,..in the center of the strut,..you have the jury strut which does buffer vibration,.. at the point that the jury strut is attached,..but ..because both ends of a repair in the middle of a strut would be exposed to that vibration ,..more so then an on end,..and welds are very suseptible to vibration,..there is allot going on there at that point ,..wind induced vibration at speed being the major culprit,..personally I would not repair a strut in the middle ,and get that warm and fuzzy feeling ,..I would get a new piece of 4130 and rebuild the strut before welding it in the center.
that is just my personal feeling about it.