Hello there Eric!
Regarding the accuracy problem, there is actually a bug in our plugin that appears when you use different screen and render resolutions. The plugin will only read the screen resolution, so you can get pretty severe diffs depending on the difference between screen / surface resolution. This problem will only appear in fullscreen modes though, so if you are having the problem in the editor it’s probably just a bad calibration like Jenny said 🙂
I have made a fix to this, I just haven’t had the time to make a pull request yet, but I’ll post the diff below.
When it comes to deriving from the sample actor bases etc. it might not be as easy as simply deriving from it. I haven’t looked at that for a bit, but you might have to hook some stuff up as well to get the expected behavior. I would recommend checking out the code and mirror what is done in the sample.
If you can explain more in detail what you want to make, I might be able to provide you with a BP-sample that works for 4.7!
Link to pull request that fixes fullscreen differing resolution bug and some other stuff: