When creating a 3D representation of a tesseract, the size of the inner cube relative to the outer cube is arbitrary and can vary based on artistic interpretation. Different proportions can illustrate various perspectives of the fourth dimension, but there are no strict rules. For 3D printing, the thickness of the connecting lines between the cubes is also flexible and should be determined by practical needs rather than mathematical accuracy. Ultimately, the focus should be on achieving a visually appealing model. The design choices are subjective and can enhance the overall aesthetic of the tesseract representation.