When you work in HOn3 the laws of physics are on your side. The highest stresses, those that take the material past the yield threshold, come from only few sources:
1. Handling by outsized giant beings (1:1 humans)
2. Thermal stresses from dissimilar metal expansion and contraction due to exposure to hot (summer sun) or cold (parked car on a Minnesota winter night) environments. If the whole structure is brass that's no issue. Note here: work hardening of materials has no effect on their thermal expansion properties.
3. Over tightening screws with not enough threads to support the load. Engineering rule of thumb here is thread depth at least the diameter of the screw; better 1-1/2 times the diameter. Not the same for plastics. They vary. Most likely source of problems is with coupler pocket screws into short threads in thin brass.
Best bet here is to anneal the brass before machining, if you can, and learn how to get clean cuts in the gummy soft brass. That's another subject.
FWIW -- Ed Weldon