A song written for High G can almost always be played on Low G when it comes to chord melody. That's because the melody is played with the thumb and the highest note is the melody. The Low G doesn't impact that, and Mike's arrangements never call for the use of a G as in Campanella playing.
Low G arrangements don't work as well on High G...because the melodic line has the freedom to go down to G under middle C if necessary (whereas songs written for High G stop at middle C). If you want to play through some Low G arrangements, check out the incredible work by Spencer Gay at ukeeducation.org.