@Visualize
I also had a
very quick look at deferred meshes in Modo902 with V2.5 of the Octane plugin, and while it seemed to work ok, I opted to use instances for some reason instead (I think it was just easier). Have you tried playing around with 'Display' --> 'Draw Options'? I use this with all my high poly trees and it speeds up openGL IMMENSELY. Can add to your mesh and/or all instances, even with a scene full of high poly tree meshes and instances openGL is still very fast. And enough detail visible for accurate composition in openGL.
Typically I use these settings for a high poly tree:
Which will look like this:
If you need even more openGL speed, uncheck 'wireframe' and things get very fast:
You can assign a different colour/tint to groups of trees for easy visual feedback: