We finished up the mailbox installation today. The numbers that I bought for the post all needed to be trimmed down on each side so that they fit in the recessed area of the post. R used aviation shears to cut the aluminum plates that I purchased the other day. They are made of aluminum so that should make them maintenance free, which is what we are going for in this mailbox/post installation.
Might even add some day lilies for summer color. I have some of the day lilies plants from R's childhood home. They might contrast nicely with the post because they are very tall and pale yellow. Plus, they are an older variety which is more age appropriate.