Is A frame notch always NECESSARY?

[leftybass209]

Short answer: No.
Long answer: It's dependent on your particular case.

This is one area where the guy across the country really has no clue what you have, or what your requirements are. I've seen people measure out their drops and have anywhere from a 1/4" to 3/4" difference between distances from the bump stop to the axle tube. (I'm not saying that is the distance, just the difference in measurements) That tells me one very important thing; every truck is different!

Fortunately this is one of those instances where, if you like the 4" drop, do it. If then, it seems too close for comfort, you can add a notch later. I understand you don't want to make too many modifications, and chances are highly likely you won't need a notch on 4 inches unless your truck has led a really rough past life.