Hello, couple of thoughts …
– Perhaps your gallery software can be “told” to ignore thumbnails with a certain prefix?
– Here is the line from admin_functions.php at around line 251 that determines the destination of thumbnails. I wouldn’t really recommend it, but you could modify it:
$thumbpath = substr($file, 0, strrpos($file, ‘/’)) . ‘/thumb-‘ . $path[count($path)-1];
$file holds the entire path – including filename – of the large image. So what it’s doing here is chopping it down to just the path – no trailing slash – then inserting /thumb- and adding back on the large image filename.