All you need is 24kbps if your using G.729(A) CS-ACELP compression... (Wild Blue Value pack gives you 512kbps of bandwidth down and 128Kbps up...) more then enough to run any known reasonable compression for VOIP which typicaly ranges up to 80kbps...
Have you used G7.29a before? Reminds me of the days I had Packet8.... Once you go g711u you can't go back!
Not to mention the latency of the satellite connection. VoIP over satellite is useful if you have no other means and thats about it.