Force and Space

Betza's Law of Force and Space in Chess Variants says:

The relationship of the amount of force on the board to the amount of space on the board is important to the character of the game, the "feel" of the game.

More force makes the game shorter in terms of number of moves per average game, but it also means that you have to think more for each move. (The game is more strategical than tactical.)

All of my old variants, from the 1970s, were designed for postal play, so they had a higher ratio of force to space than you see in FIDE chess.

The amount of force on the board must be measured relative to the strength of the King.

Force and Space in Three Dimensions

The simplest form of 3D chess would be to have an 8x8x8 board with 8 full sets of pieces per player.

Many of the 3D chess games I've seen have extra space added to the board, but use the normal allotment of pieces, or only a few times the normal amount; I feel there is too much space for the amount of force.

Pawns in Space

Pawns are a problem on bigger boards. On a two-dimensional 10 by 10 board, Pawns don't feel right. 8 squares from end to end, that's what Pawns want.

In order for Pawns to feel like Pawns, they need to form an unbroken line at the start of the game; in 3 dimensions, they need to form an unbroken vertical plane.

Smaller than 8x8x8

If the board is smaller than 8x8x8, then a Rook or Bishop will be able to travel its full distance on a plane, but will be limited in the third dimension.

This is okay, and perhaps a 3x8x8 or a 4x8x8 game would actually be easier to play; but, once again, I have to stress that I'm searching for a 3D Chess, not just a chesslike 3D game.

I am pretty sure that 8x8x8 is the only correct size for 3d Chess.

Is Half a Cube Equal to Half a Plane?

One assumption I have made is that putting the "standard" number of pieces on every level leads to a "standard" balance of force and space. In the initial position, half the board is occupied.