Disable download of full-sized pictures for guests AND other groups

[boke78]

Hi,

I've just installed Paver's plugin to control full-sized picture download.
I still have 1 big problem with this.
I can configure a group to have download permissions, but the permissions count on every album.
The objective of the site is to grant download permissions to clients, but they may only download pictures of the collections they sell.
For example: a mercedes dealer should only be able to download full-sized pictures of mercedes, where a BMW dealer may only download full-sized pictures of BMW.
Guest and other groups should be able to see the thumbs and normal-sized pictures.

Can anybody help me with this, 'cause putting users in other groups etc ... doesn't seem to do the job.

Thanks a lot in advance