NEED HELP ON SALE DIGITAL GOODS - STL FILE FORMAT

I am setting up a shop to sell digital files. These digital files are 3D drawing files in stl format.

Tried upload stl files in the download section It fail to upload.

Wonder what I need to do to ha OC version 2.1.0.2 accept such file. Tried other files like pdf it worked fine.

Any help is greatly appreciated.

Thank you/William

Part of the problem solved.

Added MIME and stl and model/stl respectively to allowed extensions and allowed MIME in Settings/Server.

Now trying to solve how to upload files of larger size. Direct upload not possible because of encripted codes are not attached to direct uploads.

What do I have to do to allow uploads of say 100,000kb?

Any help is greatly appreciated