@ got armour: No, I hadn't seen that tutorial before, but after seeing the vid in the first post, then playing the level myself, I knew that's how you had done it. Trouble was breaking through the glass ceiling. If I can get that down, it'll be much easier than trying to launch myself up the dock side of the base. I think that method requires two people anyway.
EDIT: WOW. I finally made it up there. That crap was HARD. First I had to deal with getting over the ceiling and to the back of the Pelican, then I had to deal with timing the Armor Lock right so it didn't run out too early. THEN, I had to time the jump off the Pelican right so I didn't die when I hit the ground... It took me about two and a half hours to finally get to the turret. Too bad you can't enter it... On the bright side, I got a close look at the bullets used by the turret. Those suckers have to be around a foot long! .50 cal on steroids! Anyway, thanks for the tutorial.