I really liked the THWACK and u/Overthinking_R_Us's remix making it into a double octagonal head. Though, I felt they all needed to be a little longer, so I did that.

I also wanted to make the head solid and the handle hallow, so I cut the pieces in twain and used CURA's per model printing to make he head 100% infill, and the handle __% infill, and printed them together. There is a slight line that can be seen where the two models intersect, but oh well it's a tool and I'm sure someone brighter than I can fix it if they wanted to.
The split models also means you can make the neck a little longer too if that's what you desire.

There are 4 files:

First, is just a 15mm longer hammer.
Second, is the project file for the meshed solid/hallow hammer
Third, is the head/neck region if you want to make it longer or have a preference on stitching.
Fourth, is the handle for the same reason as the head.

Voxelabs Aquila

Doesn't Matter

Yes

.15-.4

20-100

I've printed this on a .4mm nozzle and a .8mm nozzle and it came out great both times!
Amazingly the .8mm nozzle printed without supports after forgetting to turn them on. I was quite surprised by that.