I had flattened the bottom of the bench top so that it could sit flatly against the aprons, but I was not obsessive about it as it only had to be completely in plane where it contacted the aprons and the cross members of the base.
The top I wanted to be completely flat as I was going to be referencing all my work off of it. I know that it is wood and wood will move, but I was determined that it would move from a flat reference point. It became a battle of hard maple and me. The maple almost won out, but my opponent underestimated my staying power.
I first started off with my #8 and my #4 both set with rank cut. The #8 I ran across the width tying to get it flat that way.
My belief is that you have to make a surface concave before you can make it flat. I concentrated on hollowing the center out. It takes quite a while to make something concave but little time to make it convex, so I stayed clear of the edges for the most part. I used the #4 to hit some high spots.
This hard maple was chewing up blades edges on my A2. I had to up the bevel angle to keep some decent edge retention. I was popping blades out quite often.
I then shifted over to my #7 set with a fine cut to prevent tearout as I started to fine plane the both the width & now the length. This where I really ended up pulling the blades for resharpening. A couple time of doing that and I got really smart when I remembered that my #4.5 had the same blade as my #7. Now I was hot swapping blades and the top rolled over and submitted.
Here I am running a finishing pass with my #4.5.
I have checked the top and it is flat. There were time during the process I doubted my sanity, but now it is over I feel it was worth it. Below is the evidence of my labors.
On the next bench, I think I will use something a little softer than hard maple.