so I started to poke around in the cfg files just for giggles and ive notice something.
C:\Program Files (x86)\Steam\steamapps\common\Kerbal Space Program\GameData\Squad\Parts\FuelTank\adapterTanks
im running 1.3.1, stock install. if you open up the mk3-size2 for example. note the mass. (1.79)
now open up mk3-shuttleadapter. and again note the mass. (0.7)
start ksp and compare notes.
in game -->shuttleadapter mass: 0.7
in game --> mk3-size2 mass: 14.29
this cant be the only discrepancy like this too. anyone got any ideas?
a quick install of KER confirms mass is 14.29kg for the size2 adapter