I like your Poster, but I might suggest putting dark cloth on the walls you are close to as to avoid reflection off the walls from the enlarger light. It can cause a bit of fogging on the paper or a loss of local contrast in the image.
I'm adding an example...
See the first or 7th picture as an example of what I am talking about.
If you can't you will live without it, but I think that close to the corner you will see a difference.