Can anyone give me a pic of the Gargant?
The Inferno mod is too large for me to download, so I might as well forget about playing

As for it having no vulnerabilities......I find that impossible to believe.
everything HAS vulnerabilities, no matter what you may think. This ship is super-large, which, although not a major weakness, is still a
weakness nonetheless. A super large ship like that is going to take time to move around, turn or what-not. Attack it from behind and you might get hit by Anti-fighter beams and even other beams, but it is still valid! Hit the rear with as many bombers as possible; knock out the beam turrets and engines with Several hundred bombers (yes, the GTVA CAN mobilize that many). Moving ahead and sending a wave of bombers or even really quick Capital ships to do beam strikes against the Sensors and Nav subsystems would be optional, but preferred. With Sensors out, they wouldn't be able to see what was coming.
If everything goes according to plan and provided not too much goes wrong, the ship should be disabled for a short period. Now, hours (possibly days) before the Super-ship even jumped in, you clear the nearby asteroid asteroid field, strap tugs to asteroids and somehow jump 'em near where the node is and send them at full throttle at where the Super Ship might be in a few hours. Just to be sure, you take a hell of a lot of tugs and keep throwing 'em at the Node. Throw enough Asteroids (enough of the really large ones) and the Shivan Capships around the Super-ship will be distracted a bit into stopping them before they can cause damage.
Now, if the Super-ship has been disabled and sensors shut down (even temporarily) this would be the perfect oppurtunity to do a quick strike with just about any Cap Ship around. Although the Exterior armor may seem thick, if beam cannons are concentrated at just one point (And i mean
exactly one point) it will be enough to create a large hole. Dig deeper and deeper with beam cannons, and the hole should become larger. If all beam cannon fire is concentrated on the same spot above the reactor, Eventually the weapons fire should be enough to bore down and reach it, destroying it.
Worst comes to worst and the Super-Ship has several more reactors, or even manage to contain the explosion of this one, you do realize that you have a huge hole in the Shivan's hull, through which you can send Fighters, Bombers and even an Argo transport carrying a Meson bomb or some huge explosive. This should cause even more extensive damage, and the fact that the ship is so huge means that Fighters and Bombers could probrably send missiles directly into the ship, by-passing any armor and such.
Goddarnit....i've been ranting again........
