The more time goes by the more I see some of the game's most experienced players saying that there is little need or advantage to worrying about making width come out to en even multiple (or fraction) of 20. Odd sizes are perfectly fine if there is a good reason for building the unit the way you did. This reason may be one of economic efficiency or of countering a specific enemy threat. IMO, maintaining a good balance between your factory production, your resource availability, your equipment stockpiles, as well as needs in the field far outweighs the value of width considerations.