I don't know which rods are you talking about. They have the dimendions they have becouse that was what I happened to have around. Everything is like it is for a reason, a servo may seem easier to control (it is not, really, a solenoid can be driven using the spindle enable on pretty much any version of grbl) but will be much slower in operation and wear out much faster. Stepers are placed on different sides for space isues and to allow more air to flow around them, not concentrating heat on one spot (they do get hot, even in this light duty aplication). Having said that, I encourage you to make any changes you wish, and please make sure you publish them.