I agree. Adding blocks that do not generate lift will hardly increase the drag. If you add only a few blocks, you will get sufficient accuracy without changing the drag value.

I mainly want to add some decorative lights, I feel that adding a small amount of decoration has little impact on the hit (can't be wing blocks)

Drag of projectiles included in this item has already been measured and is indicated on the Paintable Signs in this vehicle. If you want to know the drag of other projectiles, you will need to perform parameter identification using tools such as Excel or Python.

How to calculate Drag