Giant Cream Puff shells
You haven't really explained what you did, so it's a bit hard to give useful advice on how to overcome a failure, but my patê à choux pastries have always come out sized proportional to the amount of pastry I use.

Since choux doesn't tend to spread much, make sure your base is close to the diameter you're after; I just pipe inside out, creating a connected spiral, until I reach the desired diameter. I continue piping inward through the middle of the original grooves. My preference is to make tiny ones, but if I needed to make larger ones I'd just continue spiraling in and out as needed until I get to the point where I only have a "tip" left. With a typical Ateco extra-large tip you'll probably get about an inch of puff for each layer, so you probably just need about 3 layers, because you can probably compensate with an overstuffed filling. With more layers than that you may lose structural support.

Some "giant" cream puffs I've seen online just used a large ice cream scoop, but I think that'll probably only get you to about 3-4" diameter at the most. If you don't like the piping approach, you might cluster three scoops near each other and wet-pat them so that they touch.

From then on, it's just a matter of adjusting time and temperature. Larger ones likely need a longer baking time. Additionally, larger ones may benefit from a larger proportion of egg white to encourage a bit crisper outer layer.