Marauder & original Behemoth elbow joints are some of the worst to work with...
While most of my MAD's have been OK, I have also had to do this with, easily, 25-30 of them. Because of how soft the old RP lead was, most of them are toast after one drop.
For Marauders:
1) Measure the length of the arm pieces.
2) File down the jointing so you have two flat surfaces.
3) Use a small diameter pilot drill into both lower and upper arms, doing your best to keep it parallel to the 'line' (through the arm).
4) Measure out a length of paperclip or other piece of steel wire; Bend at about a 100-120 deg angle in the middle, or, at the point which would reconstruct the elbow-angle.
4) Drill to a .05-.1mm greater than the diameter of the wire.
5) Check-fit the lengths to your original measurement, then trim the wire, or drill as necessary.
6) Glue, and try to preserve the previous arm-length as possible.
7) Reconstructive surgery with Green Stuff or other epoxy *PUTTY*. Pro-Tip: The MAD's have a type of slotted pattern that run parallel to the arm; Take a pair of needle-nose pliers or tweasers, and 'roll' the teeth onto the soft Green-Stuff (See pictures; Use of the tweasers-tip perpendicular to the arm will give you the correct pattern); (image of MAD "courtesy" of whomever painted it).
