Hi Phil,
When creating a Forest object / using a spline or surface, always check the coordinates - they should match the intended orientation. For example, a spline or plane created in the Front view will behave differently in ForestPack than one created in the Perspective or Top view.
If you want to change it, you can use 3ds Max’s Rotate tool just as you would with any other object. For splines or surfaces that have been reused or imported, it can also be helpful to apply the Reset XForm utility to reset their local coordinates.
I hope this helps.
Best regards,