What would be considered deep experience with OpenCV?
also, assuming you have said experience, is there a function somewhere that lets you do a findHomography with ransac, but lets you assume there's no perspective transformation? estimateRigidTransform seems close, but doesn't like outliers?
You should be comfortable enough with OpenCV that you can extend or modify it as needed, to accommodate additional use cases that are not within it's current functionality.
edit 2: solvePnP should give you what you need for your second question.
also, assuming you have said experience, is there a function somewhere that lets you do a findHomography with ransac, but lets you assume there's no perspective transformation? estimateRigidTransform seems close, but doesn't like outliers?