So . . . . Here are some pictures to explain the issue:

1st Attempt:

Driveway using diff object, in menyoo (https://imgur.com/hMQYMnc)

Driveway ruined, converted from xml to YMAP (https://imgur.com/ONPo9yQ)

Attempt 2:

Driveway created with menyoo spooner (https://imgur.com/UZAOjVx)

Driveway ruined after converting xml to YMAP (https://imgur.com/EiI4nQ6)

in case the pictures aren't clear enough, driveways that I create, using 2 different "road" objects look pretty decent after I spawn them in using menyoo's object spooner. I then convert the xml "map" into a .ymap file using ME2YM, and shiiiiiii , it appears that the "pitch" and "roll" manual placement values are ignored/bypassed. The odd thing is, no other objects spawned (over 900 of them) seem to have this issue.

Anyone know why this happens? Any possible workarounds/fixes?

Thanks in advance!

ps: please ignore the mediocre fence placement alongside the driveway.

@chonkie Interesting stuff man, I looked up mlo interiors and it seems that mlo's have collision mapping and whatnot to prevent props from disappearing. Yeah, it does seem like a lot of work, but worth knowing about if I ever start making my own maps.

I think I'll just stick to figuring out how to edit ymap files, since I just need to add some rug objects to the floor and voila! Cars remain in place. I wish I understood why lol.

So I've installed a couple ymap format houses and they load in the world just fine. After getting a couple vehicles to them I wanted to see if I could use vehicle persistence mods to save cars in the garages. But to my surprise, they fall through the floor! At first I thought it was just one house, so I tried another one; same problem!

I'm using Map Builder 1.04 Community SP. I've double checked my dlclist.xml and all my other mods are working just fine. This seems like a very specific thing, because if the cars can't remain on the ground surface of the ymap house, then how how come I can't fall through?

If anyone knows a thing or two about YMAP objects and cars, any help would be appreciated.

also, I'm running GTA V (version 1.0.1180.2 standalone) and I updated OpenIV, ScriptHookV, ScriptHookVDotNet.

(UPDATE)
so I've discovered that cars will not fall through the floor if there is a carpet or rug present. So. . . . that's cool, if only I knew how to add carpets to the garage lol.