Deleting the base collision, and using built from the builder brush collision?Is it possible with speedtree models? Or maybe this? http://forums.epicgames.com/threads/759698-SpeedTree-Collision-problems-And Maybe you just need to play with the settings more.
Glad to help :) heres my Tree Properties, I think that's what you wanted http://postimg.org/image/9lmzyopdd/full/ SpeedTree Model - http://www.mediafire.com/download.php?2sf0fxyedsikel1
I dont think that. If you tried all the options in speedtree, and nothing working, then i recommend to make your own tree in a modeling software, so you can use your custom collision for it.
Have readed this link already. done same, actually its only 1 wey to add collision. I think its not speedtree soft prob. its something with udk. but its just my guesses.
If your referring to the fact that the collision is off, thats my bad I was messing around with the Randomize in SpeedTree Modeler so that one is wrong link heres the fixed one. but if you've fixed the problem its all good http://www.mediafire.com/?jchlo3fn5mnw2qg
In image you can see loaded Billboard. there is collision. So from one side you can walk into tree from other can't touch tree. So how to fix billboard place, that it loaded in same place as actual tree. I think collision is done with billboard, so i need just to fix billboard.