I¡¯ve never had any luck with any Chinese radios using VOX and anything packet, although the UV-5R and md380 are the only ones I¡¯ve tried. I ended up using my tnc-x TNC and creating my own cable. This worked great when I tried using Xastir but I haven¡¯t been able to do anything packet related for some time now. If a hardware TNC is feasible, here¡¯s the instructions to build a proper cable:
http://www.tnc-x.com/Baofeng.htm
Jay
73 de N0SR
JaySheepdog