The dimples do look underdone. It is nearly impossible to over-dimple with hand tools. With the old C-Frame you violently whack the dimples dies with a hammer.
The DRDT-2 does a nice job when set correctly. Compare the DRDT-2 dimples to dimples made with your other tools, i.e. hand or pneumatic squeezer, pop-rivet dimple dies or vice-grip dimple dies.
Make sure you have set the DRDT-2 to go over-center, but not so much pressure that you stress the mechanism.
You should expect to see a slight halo from the outer edges of the dimple dies on the al-clad.
RV-7A - Final Assembly