That's interesting. I did an order with CSG early on and was impressed with the slabs and the service.
The slabs are the same size as PSA's, within a millimeter of thickness. I use Superior Fit Innovations sleeves for my slabs and the CSG slabs just fit into the PSA sleeves, which means they are nearly identically sized.
The cards I got back that were odd-sized were securely sealed at four points in the sleeve, like a Beckett slab, not rattling around.
I don't find the flip distracting at all.