Approved flex lines for propane in use in every RV with a slide mounted fridge or stove. So I don't think there can be an issue. The only thing that may be an issue would be the location of the inside connection; it should not be in an enclosed area. So any propane leaks at the connection could vent to the outside, of the RV, or flow to an area with a leak detector. You don't want any leak to be able to build up to explosive levels. Proper testing for leaks, working leak detector and your off.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.