Re: Vertical-align product images...
I'm not sure if there's any way in the Grid mod itself (never used it) but you have stumbled upon one of the most aggravating lapses in sanity of the CSS designers. Why the heck didn't they implement a vertical align element?!?
There is a workaround, sort of. Given a single image of known size and a container of known size, the trick is to divide the height of the image in half, then use that figure to locate the image's center point within the container using a negative margin. But I can't imagine the horrible mash of code you'd need to do that for all of your images in rows and columns.
Your first fix was much easier: make your images all the same using white space.
What you're actaully doing -- logically and visually -- is displaying tabular data. Sure the "data" is images, but it's still tabular data. So there's no real reason to avoid the use of a table. And it's sooooo easy to vertically align in table cells, isn't it?
Breakfast: the most important donut of the day.