Just for those who want to use voipc, I have found Skype to be the best yet, with least effect on fps, and superb quality audio. Only rules are, you need to all start together as a conference on Skype, before going into MP mode, for this I use FSHost.
If anyone is interested, and has any questions, I'll do my best to answer them. Please understand though I am still a novice with fs2004, and MP. And do not have much understanding of ATC, or other technical flying procedures. So far I only MP Fly for fun, and experience.
i use skype as well but it slows it down quite a bit
Well I must update/revise my first posting on this subject. Skype does work, and yes there is a slowdown. Have been trying other alternatives since that posting, and have now settled on Ventrillo, have found this to be the easiest for me to date. And sound quality is good.
My present problem is fs2004 itself, seems to have become very erratic, even in solo mode. And have found that my joystick, Cyborg Evo, is not apparently officially recognized by fs2004. And it refuses to acknowledge any of the available profiles.
CH brand appear to be the most compatible, more expense!