Shazza I am quite sure that if you use the unibit again (in a forward direction) it will clean up that hole quite nicely.
Just don't push to hard or you will go down to the next size, which from the original photo you might need to.

As to your question on the rads.
To this I can only guess.
However I would thing/guess that by using the 'triple in the bottom and dual on top", this would give you the best out come.

I am sure someone else here has tried this and would have real life knowledge.