COM? If your orbit was 70kmx70km, and the truss went down the physics range (22.5km), You might be ripped apart. The drag at 47.5km would rip the truss away and you would lose your orbit.
Use an SSTO to bring a C-Class asteroid back to Kerbin? As impossible as it seems, it could happen as long as we can use the asteroid as fuel. With the smaller ISU coming in 1.0.5 it might be even easier than ever.
When you forget RCS on a module to dock on to something. I cannot tell you how many times I forgot RCS and stopped playing KSP for the rest of the day.