I'm not sure where you could buy filon sheets. Filon sided Sunlines were built by simply hanging the sheets of filon on the studs and gluing them on. Many manufacturers, especially in more recent years, vacuum bond the walls together on a table- basically they take aluminum framing, fill it with foam insulation, put gobs of glue on the back side of both the inside luan panel and the filon sheet, and then suck it all together with the vacuum table.
While the filon siding does delam, more often I think it does it from water getting behind, which can mean even bigger problems.
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9467.8 (as of 5/26/19)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR