Oldtimer - thanks for the input, what you said here
In short, without visible external indications it’s almost impossible to gauge internal structural integrity.
is why it seems strange to try and repair such a complex structure as a tail boom rather than replace it. I know the answer will be cost but losing an aircraft (which is what would have happened in this case had it got airborne and then suffered the failure) is so much more expensive.
A very good friend of mine is something of a composites guru but his area of expertise is maritime based as he repairs all the lifeboats for the RNLI. If a lifeboat is crunched he often has to replace much larger sections of the vessel than were obviously damaged, just be sure that any unseen damage is removed as well.