The 4 sheet trial method was not providing me with a true feel for what I would be doing so I dug thru the scrap box until I found an angle almost exactly like the aileron hinge bracket. As I said before, I set and drilled each of the three holes 3 times each. The trouble I was having was due to the fact that the part was too small and wasn't stiff while I was drilling and driving the rivets and I was still able to get a good result.
So, after driving over 40 rivets and drilling out who knows how many - I have worked out the process and have gained the confidence to move forward with the SB modifications.