Hi axelrotter,
The open world kite demo assets are very high poly and have many very hi-res texture maps (2-4k) applied. Trying to add assets like this will cause a lot of hang time. I would recommend that you use one of the LODs for the static mesh instead and lower the resolution of the textures used. Let me know if that helps.
Just to be safe I plan to test these assets later to make sure nothing is broken.
hope that helps,