I don't think you have to ignore it, kesi, just try to make Korriban your third or fourth Star Map planet. In that case, you'll be able to do Carth's side quest parallel with the main mission, and not lose the romance subplot. Just make sure you have conversation #9 with Carth after finishing the Dustil quest (#7) and
before getting the fourth Star Map.
At least I hope it should work that way. I haven't really tried it yet, since this topic is the first real shred of proof I haven't gone all the way with the subplot, and I haven't had time to replay the game yet. But theoretically, I guess if you do everything it says in yoyopogo's link and
not have Korriban as the last planet
and finish Carth's side quest before getting the fouth Star Map-
Ok, I'm starting to stray... You get the picture.
Resumé: Do everything nice and proper, in accordance with yoyopogo's link, blah blah... Talk to Carth (conversation #7) any time before getting the third Star Map. Get off the Ebon Hawk (with him) and you'll meet the bloke who starts off the Dustil quest. Go to Korriban (make Korriban your fourth planet, e.g. Dantooine, Tattooine, Kashyyyk,
Korriban, Manaan), solve the side quest, talk to Carth twice (conversations #8 & #9), pick up the Korriban Star Map (fourth Star Map), and continue as instructed in the site yoyopogo mentioned. And that way, you won't miss out on anything, and everybody can be united as one big happy family!!
Ok, I know I'm ranting now...
EDIT: I cut it a little fine there... You can make Korriban your third Star Map planet. You just have to trigger the side quest before actually picking up the third Star Map.
Oh what the hell, you know what I'm trying to say here!! 
*sigh* You can have both the side quest
and the romance subplot. You just need to plan a bit, in order to finish the Korriban side quest before getting the fourth Star Map, and also hit #9 before getting the aforementioned Map.