There are several possible cause for very slow model loading, other than slow internet connection.
1. File size
When the file size is large, long downloading time is inevitable.
If the texture file being used has a resolution of 2048 * 2048 pixel, the file size could around 10 MB.
If you are not so picky about the resolution, you can downsize the file by 1/16 with texture resolution of 515 pixels per side.
2.Number of materials
Lesser the number of materials, faster the rendering of the model.
You can reduce the number of materials by applying single material on multiple meshes during 3D model creation.
It's a ID required to enter a specific studio.
When entering a studio from “Stream on niconico live” or “Stream on other platforms” on title screen, you will see your studio ID shown on the calibration screen.
By sharing the studio ID and entering the studio ID into [Destination Studio ID] text box in the title screen, your friends may Join the same studio you are in.
(Chose [Rooms] from the Ring menu and select [Saved Rooms] to enter the studio)
It might be the case that the file path to the VirtualCast application folder contains double-byte characters.
Please try placing the folder under a path without any double-byte characters (Directly under C drive, for instance) and see if it works.
This could be due to FastSpringBone.
Try turning off the FastSpringBone feature.
If this fixed the issue, we would appreciate if you could report this on VirtualCast Steam community.
If the problem still persists, there probably is some issues with the model data itself. Please contact the model author.