can you post the curtis hitch model you used. i have used curtis hitch on a 2002 and 2007 model prius, each requiring a different model hitch. the v looks like it will require a different model also. i use the hitch for a yakima bike rack and ski rack. obviously have been doing it a long time. the 2002 just turned 190k miles and my son still uses the bike rack. my 2007 had 105k when i traded it for the v.
i don't like the strap on carrier on the back of the vehicle as it is not as secure and prevents rear access. as for a roof mount, 2 problems, one i now have that lexan moon roof and i have difficulty lifting the bikes to the roof level.
i did haul a trailer with the 2007 prius but that was a harbor tools fold up and i only went to the lumber yard and back distance of only about 3 miles and never more than a couple of undred pounds. biggest problem was getting a wire harness adaptor, but i found one.
never had the dealer question either hitch. but in the manual the word was "NOT RECOMENDED" now the wording is "DO NOT"