Make thumbnails bigger...

[exoticsrally]

Hi guys,
Here's the problem I'm working with please let me know if something can be done.

I just installed the autoresizer mod from here, but it only works with images that are hosted on other websites and posted on my forum with [img] tags. Doesn't work with the attachments.
I don't want to use thumbnails in the attachments anymore, so I decided to up the dimensions of the thumbnails to 900 so that when the forum creates the thumbnail it'll be 900xXXX and clickable to open a new window with the full size picture.
It won't work for some reason. I changed thumbnail size to 900, then thumbnails per row to 1 and Thumbnail Creation to Yes, with borders and dimensions.
And I finished off doing this - Maintenance -> Update Counters -> Rebuild Attachment Thumbnails.

Still doesn't work.

What basicly I want to achive here is have my users attach images that will downsize themselves to say around 900x650 and be expandable just like the outside pictures that get posted with [img] tags.

Help me if there's a solution!

Thanks