Began heater installation. Since the Subaru engine is water cooled, there is plenty of safe heat for the colder flights. I started installing the heater now because I have to determine how and where I will be installing the Control Unit of the Vertical Power System for managing my flow of electrons. The most likely spot is in the forward right corner of the cockpit. Here the power runs to equipment will be short and this is the easiest place from which to route the connection cables between the CU and the Display and the Switch Panel. The problem is that the CU will need to share space with the heater and space is limited with these bulky pieces. I used a 1/2" board to raise the heater off of the floor. Tthen using Silly Putty on the firewall and a level on the heater, I moved the heated forward to determine the location of the firewall holes for the heater core penetrations. The center of the Silly Putty marks from the core tubes were marked with a center pinch. Tomorrow, I'll drill the holes in the firewall for the heater core tubes. I'll also drill holes for the bracket nutplate bolts that will secure the heater to the firewall.