re G force experienced during roll/ rotation. Surely once the rotation is complete, the overwhelming force acting on the load would be plain gravity eacting on an inclined plane.
ie classic newtonian mechanics.
So slight accel' during the T/O roll.
Slight +'ve G during rotation, not very significant.
Then, as it starts the climb, plain gravity acting on a load secured to an inclined plane added to the a/c acceleration... surely more force to be resisted here (just after rotate finishes) than at any other?