I figured out how to make a hypervelocity gun shoot a space station.
As you are probably aware by now, The imperials can not use raid fleets. a raid fleet is a small number of land units which can sneak past space defenses and directly attack the land base. But the empire does have some tricks. and yes they are very tricky to pull off on a well defended planet.
I'm playing Bryants mod 2.5G and Mara Jade and Boba Fett both can sneak past space defenses, so you have to use them. put them in the space slot above the planet you want and then move them to the land and it will start a land battle. Its wise to begin the battle with Boba fett since he has the jet pack ability and can get out of trouble easier. And mara jade's ability to force corrupt infantry to your side is pretty useful when you get swarmed. Her sticky bomb ability works good against the small hovering tanks, but doesn't do hardly any damage to the heavy tanks.
To win a battle like this where you are outgunned and outnumbered. you need to be cunning.Use the local humans to help you secure build pads and make a bacta at the upper right reinforcement point. Now your main goal is to try and get more build pads and build anti vehicle turrets on all of them and retreat back to the bacta when you get low on health. sometimes you can lure the rancor into the enemy base and cause a lot of confusion and damage to allow you to get some vehicle turrets built while all of the tanks are distracted. The turrets you build next to the building will automatically shoot at those buildings if no units are nearby. so your main goals are keeping your heros alive and building turrets.
Here is a tip. After you send boba fett to a jetpack waypoint you can right click on other areas of the ground and make him fly anywhere you want. But sometimes he can get stuck on a hill and you can't move him at all, so be careful.
Anyway when/if you win the battle. you will have gained land control and there should still be a enemy space station in orbit. I tried to build my hypervelocity gun, but by the time I looked again, their level 5 space station had disapeared. but it was there up until I had the gun built.
The cool thing is you can attempt this right from the beginning in this mod. Just go attack mon calimari since its the easiest to take over and it has a lvl 5 space station in orbit.