I tried this mod today the first time and I'm pretty satisfied. But it seems a bit buggy at my Vovlo FH16 2012 model. Doesn't matter if I chose the cabin first or the chassis, the game crashes immediately. The gamelog says:
00:04:50.443 : <ERROR> [fs] Failed to open file "/def/vehicle/truck/volvo.fh16_2012/accessory/steering_w/exclusive.sii" in the read_only mode
00:04:50.443 : <ERROR> load_unit() - Failed to open file (/def/vehicle/truck/volvo.fh16_2012/accessory/steering_w/exclusive.sii)

For MAN there are far more entries:
00:03:25.045 : <ERROR> [fs] Failed to open file "/def/vehicle/truck/man.tgx/accessory/grill_a/cab_grill_02.sii" in the read_only mode
00:03:25.046 : <ERROR> load_unit() - Failed to open file (/def/vehicle/truck/man.tgx/accessory/grill_a/cab_grill_02.sii)
00:03:25.046 : <ERROR> [fs] Failed to open file "/def/vehicle/truck/man.tgx/accessory/grill_b/chs_grill_02.sii" in the read_only mode
00:03:25.046 : <ERROR> load_unit() - Failed to open file (/def/vehicle/truck/man.tgx/accessory/grill_b/chs_grill_02.sii)
00:03:25.047 : <ERROR> [fs] Failed to open file "/def/vehicle/truck/man.tgx/accessory/light_g/l_glass_01.sii" in the read_only mode
00:03:25.047 : <ERROR> load_unit() - Failed to open file (/def/vehicle/truck/man.tgx/accessory/light_g/l_glass_01.sii)
00:03:25.047 : <ERROR> [fs] Failed to open file "/def/vehicle/truck/man.tgx/accessory/side_g/c_glass_04.sii" in the read_only mode
00:03:25.047 : <ERROR> load_unit() - Failed to open file (/def/vehicle/truck/man.tgx/accessory/side_g/c_glass_04.sii)
00:03:25.048 : <ERROR> [fs] Failed to open file "/def/vehicle/truck/man.tgx/accessory/back_1st/b_look_02.sii" in the read_only mode
00:03:25.048 : <ERROR> load_unit() - Failed to open file (/def/vehicle/truck/man.tgx/accessory/back_1st/b_look_02.sii)
00:03:25.048 : <ERROR> [fs] Failed to open file "/def/vehicle/truck/man.tgx/accessory/xenon/lenticolare+leds+blk.sii" in the read_only mode
00:03:25.049 : <ERROR> load_unit() - Failed to open file (/def/vehicle/truck/man.tgx/accessory/xenon/lenticolare+leds+blk.sii)
00:03:25.049 : <ERROR> [fs] Failed to open file "/def/vehicle/truck/man.tgx/accessory/rear_light/fullled.sii" in the read_only mode
00:03:25.049 : <ERROR> load_unit() - Failed to open file (/def/vehicle/truck/man.tgx/accessory/rear_light/fullled.sii)
00:03:25.055 : <ERROR> [fs] Failed to open file "/def/vehicle/truck/man.tgx/accessory/extra_001/extra01a.sii" in the read_only mode
00:03:25.055 : <ERROR> load_unit() - Failed to open file (/def/vehicle/truck/man.tgx/accessory/extra_001/extra01a.sii)
00:03:25.056 : <ERROR> [fs] Failed to open file "/def/vehicle/truck/man.tgx/accessory/plate_light/white.sii" in the read_only mode
00:03:25.056 : <ERROR> load_unit() - Failed to open file (/def/vehicle/truck/man.tgx/accessory/plate_light/white.sii)
00:03:25.056 : <ERROR> [fs] Failed to open file "/def/vehicle/truck/man.tgx/accessory/light_g/l_glass_02.sii" in the read_only mode
00:03:25.056 : <ERROR> load_unit() - Failed to open file (/def/vehicle/truck/man.tgx/accessory/light_g/l_glass_02.sii)
00:03:25.057 : <ERROR> [fs] Failed to open file "/def/vehicle/truck/man.tgx/accessory/extra_004/extra04a.sii" in the read_only mode
00:03:25.057 : <ERROR> load_unit() - Failed to open file (/def/vehicle/truck/man.tgx/accessory/extra_004/extra04a.sii)
00:03:25.057 : <ERROR> [fs] Failed to open file "/def/vehicle/truck/man.tgx/accessory/rear_light/base.sii" in the read_only mode
00:03:25.057 : <ERROR> load_unit() - Failed to open file (/def/vehicle/truck/man.tgx/accessory/rear_light/base.sii)

Just to let you know. ;)