Hello; For what it is worth there was a post some time back with a picture of some filled large tanks resting only on the ends on stacks of blocks.
It may be that you do not have a serious issue, but as already stated do what makes you comfortable.
I have used iron stands for many decades. I have placed a sheet of plywood between the standand the bottom of my tanks quite often and have placed tanks directly on a stand.
My feeling is that it is always best to have a tank evenly supported if possible. I am sure that there has been some small variation from time to time but I do not recall ever having a visible gap such as you picture..
It may be that if the ends of the stand are fairly true and do not induce any twist to the tank, that you are less likely to have an issue.
I have not tried foam sheets myself, but the notion seems sound and I have read several posts where members talk about using them with success.