Tyler, when you attempted to make a domino this way you said that you had to cut a lot. did you mean off the inner cube? I've been looking at the plans and noticed that the edges of the inner cube would have to be somewhat shaved for the outer centers to pass by. Is this what you meant, or are their other problems that I'm not seeing?

It all must be shaved...
The "top layer" must have the following. The bottom is identical.

Corner pieces: 2 whole sides must be cut out, as well as the central part. Leaves room for the corners (center cut) edges (2 sides cut)
Edges: the inner part must be cut out, or lowered, if you will. Makes room for the centers.

Second layer: You must Round this layer.
Edges must either be rounded (optimal) or cut at a 45 degree angle. Centers: probably no rounding needed

I hope you understand.. I used to have a pic of my attempted kernel, but i deleted it off my server. Ill check my email, see if i had sent it to anyone

Well, in the evenings. Expect 2 hours of progress per day. I'll post pictures of the kernel and edges before I glue it all together.

I've found some of the same things as Tyler: the middle layer's corners need to be rounded off (45-degrees seems strong enough with the cubies I'm working with). The corners need lots of plastic removed - I've been turning each face 45-degees then removing the inside "half" of the corner cubie that protrudes. Since you have to do this twice almost 1/2 of the total plastic is removed from the corners, leaving them rather spindly. I'm going to see how it holds up - if necessary I may fill the gap with epoxy/putty.

One bug difference from Tyler using the $3.99 cube 2-pack from Walgreens: my center caps are not flush with the inner kernel; there's a 2.5mm spacer needed, just like the spacing required for the edges on the 2x2x3. This is a tremendous help, since the pieces need much less trimming - in fact, I have probably over-trimmed pieces and can go back and make even stronger corner-kernels.

I'll keep everyone posted.

You are right.
The inner pieces need shaving for outer centers AND outer edges. ALOT of shaving is required, and the inner cube becomes unstable. I dont know if fisher's 2x3x3 is so great... a split axle is better

Note, that all my previous posts, consider the following:
the centers, edges are NOT RAISED. they are flat on the inner cube

For this one, so much shaving is needed, that i URGE you to use a dremel or other like tool. This way, you can round the cuts to take out a minimal amount of plastic away, leaving more support in the kernel

About the centers being flush,
i was working with a giant cube and 57mm cube, so i guess i had different results because of that. Its nice to know that they arent flush. easier to make i would think.
What are you using as a spacer? a Epoxy putty Buildup?

Thanks for all the info, I may try to make a split axle first... thinking about it before I start.