As K2 already has all necessary in administrator/components/k2/models/item.php for manipulating images, why not use it for Galleria main image resizing ??
It is easy to add standard PHP lines in item.php of code to get crop, resize by height/or width + crop, Crop and fill difference with color, etc...
I mean it is your code, you know it by heart. And SIG PRO can easy use functions from already existing item.php when you upload images first time.
CSS resizing is useless for Galleria. Portrait pictures are ugly that way.
Second question. Why not add some scroller with arrows to get all thumbs in one row ?
Galleria is not easy to use as image scroller above main text, if there are 3 rows of thumbs. Not so profesional.
As it is commercial script it is in your intresse to make it more competeable with other gallery scripts.
I do understand that you don´t have lust to care about your free scripts.
And thank you for so many popup engines to chose from. Really there are not so many gallery scripts that can beat it.