When the design change bug occurs for armor, you retain the bonus and set bonus that corresponds with the design. For example, if I equip the grub vest and the design changes to the ladybug armor texture, then the grub vest grants additional blocking strength along with it's original max stamina boost. If the remaining two armor slots have the ladybug texture, regardless of which pieces they are, you will receive the set bonus for ladybug armor. This appears to apply to all combinations that I could put together.
