I find the 20x24 paterson to be too big with not enough space for the print. Cesco or Premier are flat and take much less space than the Paterson. Try with these one. They might fit.
Yeah, my generic trays from b&h are smaller on the outside but larger than patterson trays on the inside. I only have three 16x20 pattersons and don't really like them. They are much more rigid and easier to pour out though.