I've had this roof for a number of years. It looks great and we have many comments about it ...BUT every winter ice forms in the valleys on the roof. It never slides off completely and builds up into huge, heavy chunks over time. At some point the chunks release and come hurtling off the roof damaging the 1st level roof below. They flip some of the tiles and bend them upwards on the way down. Every year I have to go up and bend these tiles back down. We had to move our entrance path because of the danger posed by these chunks of ice. The sliding ice and snow has destroyed our eavestrough and the flashing boots around the vent stacks allowing water into the attic space.
This roof is not suitable for a design with valleys in areas that get significant snowfalls and temperatures that fall well below zero. I'm not saying it's a bad roof but interlock must be aware of this problem and should not be recommending it for unsuitable applications.
I have called Interlock to arrange a service call to see what they would recommend. I never heard back from them. My neighbour has the same roof and also has valleys in his design. He has exactly the same problem as me.