So for example, for a rectangle that is 20 units wide by 15 units high & a desired gap of 5 units, the second rectangle should be 10 units wide by 5 units high, with the same center as the outer one. The larger rectangle has proportions of 4:3, so if it was scaled down proportionally to 10 units wide, its height would be 7.5 units, not the desired 5 units.