that's still using the 996 croped image size.
basicly, you need to change the initialization code to use a calery size that will fit in the store message div.
the available gallery sizes are:
Proportional
1024 x 768
782 x 481
163 x 92
cropped:
62 x 62
132 x 140
102 x 102
42 x 42
782 x 481
995 x 260
so if i want to use the 782 proportional gallery, I need to change the index page for the gallery to use this code to initialize the gallery:
$gallery = get_gallery(get_mediarss_url('gallery=' . $pg_id . '&thumb=62c&full=782p'));
this is telling the galery to use the 782p full size image, and 62c thumbnail.
you can experiment with using the other sizes to find one that works for you.