Bob, There are many ways to skin a cat. The system he has recommended is used in Europe. Smaller bore piping is used which reduces dead leg water, Yes there are for and against for every system. Have you considered the extra heater cost and standby losses? Can you ask him for names of people who have it installed and ask their opinion? The final choice is yours and you need to satisfy yourself that you have the right system. If it wasnt for adventurous people we wouldnt have phones or electricity. Grahame