MechJeb version 2.5.8 (the only mod I have)
KSP Version 1.1.3 (Have not upgraded so I can use MechJeb.)
W 8.1, GTX 1080, 16 GB Memory (Still plenty of crashing with a large rocket. Go figure.)
Anyway, the moment I hook up MechJeb I get a build warning (orange triangle), "Command module faces the wrong way." Of course the warning goes away the moment I disconnect MechJeb. It matters not where I place MechJeb either.