Navigate yourself over to mods > update > x64 > dlcpacks > eup > dlc.rpf > x64 > eup_componentpeds.rpf
Once you've reached this directory using OpenIV, copy the contents the belt models into the appropriate OpenIV folders.
The contents from the downloaded 'mp_m_freemode_01_male_freemode_hipster' folder go into your OpenIV 'mp_m_freemode_01_male_freemode_hipster' which includes 'accs_diff_001_a_uni.ytd' and 'accs_001_u.ydd'.
The contents from the downloaded 'mp_m_freemode_01' folder go into your OpenIV 'mp_m_freemode_01' which includes 'teef_diff_008_a_uni.ytd', 'teef_diff_003_a_uni.ytd', 'teef_diff_002_a_uni.ytd', 'teef_diff_001_a_uni.ytd', 'teef_008_u.ydd', 'teef_003_u.ydd', 'teef_002_u.ydd' and 'teef_001_u.ydd'.