Well, speaking from a lot of experience in a center that looks like a mountain or a mole hill.
I have taken the 8 diamonds apart and then cut them to size. This takes a bit of time, but you won't have a bump then.
When I have quilted them I can sometimes take some of that out of there.
Sorry not much for good news.
I'll try to post one of my latest ones.
This one had a mole hill, I didn't trim it, should have!
I stand on top of my island to get these shots, and they never turn out the way I like them to. The center has a bit of a bump, carefully quilted it sometimes can get rid of that. SOMETIMES IS UNDERLINED. :)