Thanks for everyone's input and suggestions. The solution that I decided to go with was to get strips of wood to go underneath the tank trim and sand the strips down to compensate for the hump.
I keep forgetting to take better pictures while I'm working on this, but here's what I bought to fix the problem:
The strips are teak wood which does great around water and won't require any coat to provide protection. They are just a little over 1/4" tall and a little less than 2" wide.
I'm almost done sanding the pieces to compensate for the hump and a few other minor irregularities in the stand top. There where a few spots that needed filler, so I used water proof wood glue to provide the extra depth where needed.
I've also ordered neoprene rubber strips that will go in between the teak strips and stand top (overkill probably, but I like overkill).