Transformation to vehicle mode: Turn the head round 180 degrees, fold it back and slide into the back of the turret. Attach the gun and grenade launchers to the turret. Fold the hands back into the wrists and the feet & heel spurs onto the front and back of the legs. Fold the arms up into the space occupied by the head. Swivel the legs bellow the knee 180 degrees then bend the knees. Bend the elbows. Fold each limb out so they form a cross pattern for the vehicle to rest on. Swing the turret through 180 degrees so it points upwards over where the head was and fold the front of the turret down. Fold the seat up behind the turret seating Major Tungsten in place so the hole in his back takes the peg on the seat and he can hold the handles of the turret.
The resulting "spider tank"/gunner station looks awfully like the Scrpametal drones seen in Cybertron with the addition of a chair on the back for his driver to sit it. Major Tungsten is a white suited figure wearing a beige flak jacket. He's got a small peg hole in his back, matching the peg on the seat, turning & bending elbows, hip & knees. I'm not 100% convinced that he's not meant to be Spike and they've put the wrong figure in, The "spider" has the robot leg articulation for it's rear legs, arms, for the forelegs and 2 hinges on the neck for the head.
The spider then can transform again: Fold the robot waist piece, between the rear legs, down 90 degrees under the spider. Straighten the robot legs out and unfold the feet & heel spurs. Fold the seat down 90 degrees so the back becomes the base and vice versa. Swing the turret round 180 degrees. Peg Major Tungsten into his seat and fold the spider's head down over him. Fold the hands out of the arms and pose.
The Mech suit mode isn't bad at all, integrating the human into the robot design and giving the mech suit almost all of the robot's articulation.
Far better than Icepick, Thunderhead's major minus point is the problem with the hands not facing forward in robot mode. There's no weapon mode for a larger robot to us here though. But still well worth a look when Human Alliance basics hit Argos as an exclusive.