Another thought also, I have done this in the last two trailers I have had (a bunkhouse and a toy hauler), at the end of the trunk, use expanding foam to seal the back of the attic. My Outback ended in open space, verified by an inspection camera, the Voltage had a piece of foam duct blocking the pass, but was partially blown over. I filled them through the last vents at the end of the trunk.
TV: 2015 F-350 DRW, CC, 4x4, with 14k GVWR package, 98 gallon TransferFlow Aux Tank, Timbren Shocks
TH: 2014 Voltage 3950, Sailun S637 all around