Every time I've been working on large crafts I run into the same problems. Both types of interstage seem to simply break under high load. Side interstages break much sooner, but normal interstages also break under high load. I've tried several things to fix it, including increasing the part's durability, size, and the way it is attached. However, none of these things seem to make a difference, and they still break. Is there any way to make them stronger?
Use many and paint them invisible?
Also, Try docking ports too. They used to be very strong. I have not played in 6 months or more.