WM6.5 should be fine with 3G as well as H - but may be some local issues depending on part of the world and also the Radio you have installed. I use the 0300.76 radio extracted from the original Italian ROM and that seems to be fine for all of G, E, 3G and H services in the UK. Others have reported all sorts of different results and preferences for radios all over.
You may be right. That is why I suggested Jim to try use radio 1800 which was originally released with Malezya rom which is geographically near to Jim.