First, you need to detach all four limbs before transforming.
If you can transform it with all the arms and legs still attached, you're a Newtype. -_-;;

Remove the Ex-S armor pieces attached to the body for now..

Separate the upper and lower body.

Reattach the Ex-S additional armor to the rear section, then spread the wings on the lower body's backside out to the sides.

Pull out the three locking tabs hidden inside the core block section.

First, fix just the lower body to the stand.
From here on, it feels like assembling a building — transforming each piece one by one and then combining them.
Without fixing a reference point like that, the transformation method gets really confusing.. ;

Folding the antennae, tucking in the head, and raising the chest is the same process as the Zeta/S..

Tilt the folded body section downward for a moment..

Spread the backpack out to the sides. The joints are nice and stiff, so everything locks in really well.

Then bring the body back up..

And reconnect it with the lower body that was fixed to the stand.

The connection points are completely different from MS mode.
Lock the three fixing gimmicks you pulled out of the core block earlier onto the upper body.

And like that, the center body section is ready for transformation.
Oh.. oh.. it's so complicated. -.-;; The people who came up with this transformation are something else..

Swing the backpack down, then connect the backpack support beam on the lower body to
the locking point hidden in the center of the backpack. (Once you try transforming it yourself, you'll be amazed at how intricately it all fits together!)

The backpack connection has locking points on both the front and back, so it locks in solidly no matter which direction it's positioned.

Swing the other backpack around to the rear and lock it in place.

The center body section transformed into the G-Cruiser. The way it all connects together is really something else..

Reattach the Ex-S chest additional armor that you set aside earlier.

Mount the beam smart gun on the underside.

Alright, the center body transformation is complete — now it's waiting for the arms and legs to be transformed.

The leg transformation is pretty much the same style as the S's transformation.
It might not look like much is changing, but once you actually do it, you'll be impressed by the intricate gimmicks around the front of the knee.

Attach the transformed legs.

The legs lock in securely since they connect at two points.

Transforming the arms. Remove the propellant tanks for now..

The arm transformation itself is the same as when transforming the S Gundam into G-Attacker mode.

Arm body transformation complete.

Fold the propellant tank connectors twice and tuck them inside.

Then combine the propellant tanks with the transformed arm section like so.

Arm transformation complete!

Now attach the arms.

Just like the S, the arms connect at two points, so they lock in nice and solid!

Pull the stabilizer tips forward a bit..

Then spread the wings and the transformation is done!

The Core Fighter that comes stored in one corner of the stand can be displayed alongside it.

The long-awaited G-Cruiser mode is complete~! At roughly 40cm in length, it's absolutely massive.

View from below looking up.

Together with the S Gundam's G-Attacker and G-Bomber.

Together with the ZZ Gundam's G-Fortress, which has a somewhat similar concept.
The G-Fortress is pretty big in its own right, but next to the G-Cruiser it looks almost cute;

All Sentinel transformations, gather! Together with the G-Flyers.
The photo studio is getting cramped;

Together with various transforming MGs.
Zeta, Re-GZ, Super Gundam's G-Defenser, and more..

No other transforming kit can match the sheer charisma of the massive Ex-S G-Cruiser..