Trouble with Doom

First off, best game ever made

I'm on Episode 2, Mission 8 and I'm having an incredibly tough time trying to beat the Cyberdemon on Ultra Violent mode. Can anyone give some tips on how to beat him?

(This is probably more in VeNGeD's department )

If I remember correctly is this the level with the portal in the middle and the lava surrounding it? If so one side of the level has a lot of ammo for the rocket launcher, just get that and shoot across... shouldn't be too hard. If not damn it, it's been a while since I played, if you don't finish it I will play it again to refresh my memory.