For this vessel (placed directly into orbit):
Test.craft.txt

Mass: 54314.0
Inertia tensor (diagonal): 581216.3, 44035.9, 581252.8
Inverse of inertia tensor: 1.7205296392438620e-06, 2.2708731161259498e-05, 1.7204217829091489e-06

RSC torque computed by kRPC: 25136.576576232910, 15415.692382812500, 25137.642372131348 Nm

Product of inv tesnsor and torque (that is angular acceleration when this torque applied): 0.043248638011040313, 0.35007122168601973, 0.043247408710997789

But, actual angular acceleration (full control applied) measured with expiriments is: 0.011, 0.098, 0.011 rad/sec^2. That is 4x less than computed. May be you are using total thrust for each thruster to compute torque instead of thrust/thrusters_count.