So, I have found that simply dropping the basket on a level surface creates extremely even pours time and time again, and an even place to tamp. Basically a variation of the slap shot (messed up my tamp a little as I was repositioned a little bit for the camera). Check it out.
A different angle

Do a site search for 'portafilter thump'.

I did try a portafilter thump before making the box. The problem i was personally havkng was threefold. One was that my naked portafilter is not perfectly level...total deal breaker. Second was that i sometimes canted the portafilter slightly forward and it seemed to cause the grounds on one side to be of different compression. Finally, i didnt want to use my counter top as thumper and my rancilio box has been intentionally bowed so i can keep my scale turned on inside while grinding...however letting a gentle gravity drop do the work fore has realy been miraculous for my shots.

I can imagine many people dont have my same problems though, but have been so excited by it that i wanted to share in case it helps someone else.

I do a small thump with my basket and my OE ipanema. It very frequently is not level. I see why you did it and like your idea.

I have found it difficult to keep my tapping level also. Dropping onto a flat surface seems like it's rather easier after a few trials. Thanks for the idea.