Hi iacdxb,
To solve this you need to set one Grid and one Pin. The grid should have some measurement, I used here 100cm for z, which is too large, but that is not the point. The Pin needs to be at a specific point, and this position is crucial.
Get the hi-res image to have more precision. Then place the grid on the front of that object, define z and y, even y is off. The Pin needs to be on one of the lower corners of that grid, it needs to snap.
This Pin position is the rotation point. Copy the camera, delete its Calibration Tag. Place a null object to the Pin position, do a R.H=180º so the X arrow of the axis/origin points to the backside of your object. Then place the camera under the Null. Rotate the Null R.B so the arrow lines up with the corner of the object. This might be -17º, delete the negative, and you are done.
In short: What I did here was to crate a solve for the flat part of the object, then adjusted for the angle. Done.
The workplane can be now set up to align with the given Plane, to easily add things to it, or leave the the coord-system as is and add to the scene.
There must be a reason why you do not build this object in the first place in C4D as well. Well, I had to mention it. ;o)
All the best
:o)
The scene file
https://www.amazon.com/clouddrive/share/XpLdlvnvXu93VjjbmqGfI2fI8LRuku1t5GVCUb8bDyu?ref_=cd_ph_share_link_copy
Screenshot
https://www.amazon.com/clouddrive/share/EOQre8ZcDkhnz8X0EWdg7C4Y7wWQzRscF5xCqWGQSUO?ref_=cd_ph_share_link_copy
The grid in the image is the plane set to ghost. Looks like a good fit, doesn’t it?
