What have you done?
I suppose that if you thought the RMS would not leak, maybe you would be correct. I have not tried this method of "upsidedown" or in your case UP side IN.
It may actually work.
I doubt it because of the method of insertion. Is this your second seal?
It has to go down to the base of the seal cavity. There is a ledge on the outer block about 1/16 wide that is the bottom for the seal outer edge. I do notice your block does not have my "bevel" but you MUST BOTTOM the seal below the block and not flush.
The Pelican OEM KACO seal--bottom--would work best for you. It does not have the "RIBS" on the "bottom" half and would start easier. Both will work.
Take a screwdriver in the screwdriver access slot and remove the seal. You cannot save the seal.
Begin again. The memory of getting to the seal is not worth the $20 it will cost you for another seal.
GL
John_AZ