[AngleWyrm]

Other things I tried:

I modded the boarding parties from 10 each to 1000 each, to see if it had to do with attack strength. The result was about the same: Attacker launches shuttle, they board, several moments go by.

The crew count stays at 100/100 the whole time, until the crew quarters are destroyed. At this point things happen rather fast; the crew count jumps, adding my crew to their crew. First test was 201/100(?), second test (with huge bording parties) was over two thousand/0.

Also, with multiple attackers sometimes the second shuttle will not land; it just buzzes around the target at point blank, as if there isn't room to land.

Maybe if crew were dispersed amongst the parts, instead of consolidated into one component. Will try that next.

Edit
I edited the Ion Engines to provide 10 crew each as an additional ability. As the ship took damage, crew counts xx/yy dropped from 180/180 down to 30/30 (last three engines). Ship wasn't taken, even though the boarded icon was present.

On one successful boarding, I went back (in the simulator) It had only one componant left: A bridge at 50% damage for all of 5 hit points.

Quarters
Put all crew quarters modules in front on the target ship. As soon as they were destroyed, the ship transferred ownership.

My Conclusion
Crew Combat module in SEV is not implemented; the boarding parties are supposed to be killing crew, but are not doing so.