Hey, HG, I agree with Antoine and Greg about board sizes, but I do have a suggestion that while a bit gimmicky might work. Add an extra square behind each king, place the lion there, and when the lion moves or is taken, the square (and any taking piece) is immediately removed. Hm, that would screw up your chess engines, wouldn't it? The other "preserve 8x8" option is a drop, but I do not favor that approach.