I would see if you could get them to start/date the forbearance for June 2017.
I have a friend who was successful doing this. He asked durring the initial forbearance request though.
My understanding from my reading here, is that it is difficult to get late payments removed from student loans...
About 5-6 months ago I sent ACS a "Goodwill" letter for a few later late payments that were 6.5 years old. I was denied, but they fell off my report shortly after anyways.
All you can do is try. it can't hurt anything, and you may find success in doing so.