After watching a few youtube videos and observing other machines, I decided to use harmonic drives to convert my 3 axis into 5 axis. I'm still dialing in the extra parameters, however, this 42" scale model boat hull that I pulled off of GrabCad turned out relatively decent. The machine mills within 0.1mm when milling 3 axis, so it is relatively accurate.

Some of the struggles are:

Simple alignment, which is easy on 3 axis. Not so much with DIY 5 axis. Hats off to the people who have accomplished this.
Post processor....getting the CAM program to spit out the proper sequence and defining your custom built machine in the CAM program. I use RhinoCam.
I had to beef up my z axis...pretty much re engineered it. I've killed a Z axis drive and an X axis servo in the process.
One needs a proper CAD model. I have found that 5 axis simultaneous works with surfaces, so the model needs to be engineered with CAM in mind.
Many other struggles that I'll leave out, but it's been a headache. Just one of those things where you have to keep pushing. Long way here, long way to go. At least I can make dimensionally accurate models via 5 axis now

I am milling 3+2 in the posted video. 5 programs: about <2.5hrs @ 135ipm

Horizontal Roughing from the top -5" depth 1/2" 6" long end mill
Parallel Finishing from the top using surfaces 1/2" 6" long ball mill
Parallel Finishing on right side using surfaces 1/2" 6" long ball mill
Parallel Finishing on left side using surfaces 1/2" 6" long ball mill
Parallel Finishing on back using surfaces 1/2" 6" long ball mill




DIY CNC 5 Axis Conversion 3+2 Machining EPS Scale Model Boat (4 min 16 sec)