Editing Terrain Using Push/Pull for 3D Printing

[djc87]

I am working with Google Earth terrain in Sketchup Pro 2019 but I feel my question may be more basic in concept.
I have imported topography from Google Earth, toggled the terrain and squared up the bottom and sides, to make a solid object. (squaring it up for 3d printing). I am trying to cut a shape (triangle) from the bottom face of the object and use the Push/Pull to remove this triangle shape all the way up and through the object while keeping the object solid.
The issue is I run into the Offset limits and can’t remove this triangle shape all together. I have tried making my triangle cutout before toggling the terrain but the imported file does not allow that.
Is there an easy way/(extension maybe?) to remove a particular piece from terrain?

Any feedback helps. Thank you in advance.
[mod=:1yvrv32a]The linked image doesn't work.
I've downloaded and added it again.
TIG[/mod:1yvrv32a]