My HX's had squares of that wadding (horse hair padding or felt brown stuff) packed between the frame and the side walls when I got them, light surface rust had begun under them. I was considering a clarke rubber replacement for those, (more waterproof) but the bonnet packing is a way different substance in my vans, it could be drip check, but that would be expensive and unnecessary I reckon in a rebuild, dripchek is hard to use too. Maybe later models had a compound in the frame to the sidewall, but in mine it was that wading. Compound seems smarter, but then again, it's not easily removeable once its in place. I'm liking the gyprock glue for the bonnet, it's not a watertight joint but for them sidepanels I dunno was gonna go with foam/rubber.