Probably going to have to have the front cap pulled, seal and insulate then replace the cap and seal it up again. Not sure there would be any other way of getting access to all the nooks and crannies that you can with the cap off. The insulation they put in the front cap at the factory is usually pretty laughable and strongly doubt they foam up any air gaps.
You could call Amish Family RV and ask Orvin what you would need to do, he'll know for certain.
46 Years RVing and no end in sight.
2018 Ram 3500 SB Limited, CC, 6.7/Aisin, 4X4, SRW. Comfort Ride Energy Absorbing Hitch.
2020 Cedar Creek Hathaway 34IK, Reese 19K Sidewinder PB.