Hey guys, been a while since I was here 
I read about the new biomes and the upcoming addition of the world gen files which will make it a lot easier to edit and I got some new hope into my tree project. Now the only thing I was wondering when making new trees is this:
“Do I need to stay in the old matrix for lets say the ancient oak tree, or can I expand this without problems with world gen later”
Hi @Floppy 
You’re asking if you can modify the size of the matrix in order to make your own trees to use in a mod when the biomes come, am I right?
I believe that you can use any size of matrix that you want. For my Candyland mod I sometimes modified the size because my trees couldn’t fit there so I think it’s not a problem.
Just take into account the position of the matrix (and of the model inside the matrix) so it gets rotated around its center, because trees are randomly placed and rotated in world generation (you wouldn’t really notice, but then there’s the destination / collision regions stuff, and it gets complicated).
Also, remember that trees by default have scale 1:1 with the terrain. But you can use a different scale too, only that you’ll spend some time balancing the regions. I have suffered from it 
It’s easier when the trees have default scale.
Thanks for the reply. That’s what I wasn’t sure about. When they release the patch for the biom changes and stuff do we get a option to select how big the matrix will be of our trees, so they don’t collide ? Because if the game is gonna keep the standard massurments of small, medium, big, and ancient, I would like to hold this format for my trees. I’m working on some trees atm and I feel like I don’t have enough space for it with the ancient tree matrix.
Hmm… That’s a good question. I’m not sure if they took that as a parameter, though I think that we will be able to set the density of forests (look at the desert biomes screenshots). That should help in that case.
I remember my trees colliding at first. And with the collision boxes, there were lots of troubles with trees standing on top of other trees (this happened even in vanilla Stonehearth).