Assuming the fragment has different restriction sites on each end, then I would not expect you to have many difficulties. Generally a 1:1 or 1:3 ratio (vector/insert) should be fine. Be sure your competent cells are very good and that with uncut vector you get nearly a lawn of cells (hundreds of thousands of transformants). I've noticed that transformation is frequently the limiting factor.

Try the vector to insert ratio 1:3 or 1:5 both to see which of them work. Also, be careful with the design of primers with restriction sites for overhangs. I am not sure if you are disrupting the restriction site after cloning or there will be two restriction sites if you are adding restriction sites on both sides of the insert. In that case, you have to be more careful about primers. Also, make sure, the insert does not contain the restriction site for your REs. To avoid all of these potential errors, I would recommend going for infusion cloning which is easy and avoids errors.