Testing completed. I can pull 4300kwh (358ah) before the inverter turns off from it's factory set voltage minimum of 11v and the battery still had about 48ah (12%) remaining. That makes the DoD 88% on a capacity of 406ah. I used a portable heater set on high (1,600w) until the battery reached 11.5v, set on low (800w) until battery again reached 11.5v, then used a 120w heat lamp until the inverter turned off with the battery at 10.8v.
I will be working on installing the battery under the bed, right next to the inverter and all the other electrical stuff. Biggest issue will be finding all positive and negative runs to and from the original battery bay then relocating all to under the bed. If anyone had done this to a Jayco class a, let me know where to look to find all the original cables!
2016 Alante 31v