i decided to experiment by wearing 2 abro form x plus nappies. i cut slits in the first one. i expected this combination to last double the amount of time that 1 abri x plus lasts. which would be about 20 hours. the fact is after about 14 hours it started to leak, what have i done wrong? i can clearly see that the 2nd nappy has only been used a little so i know it is not full.