Hi Greg,
Looking at your picture, it might not be needed to use a 5000x5000 size floor plane.
What you can do is created a 1000x1000 (or 2000x2000) dark gray/black Solid within After Effects, and apply 3D Reflector to the Solid. This way, with the smaller Solid size, it may cut down on processing time, and also rendering time as well.
From your picture, you may be getting the bad reflection because you have scaled the floor image. It's also possible that if you used the Replace Footage feature to replace a small image with a big image that has 3D Reflector applied to it, you may also get the effect that you are seeing now. If you are using the Replace Footage feature, you may want to use the "Use Reflections Only" feature from 3D Reflector, and make a duplicate of your floor layer. Delete 3D Reflector from your duplicate, then you can have one layer as the reflection, and one layer as the floor. You will then be able to swap out the floor with any image you like.
For more information on the "Use Reflections Only" feature, you may be interested in our newest video tutorial called "3D Reflector Fancy Reflective Floors".
You can view the tutorial from our link below:
http://zaxwerks.com/training/
Best,
Edward
