I really don't think the thickness should concern you. A 10" could easily still be mounted with a conventional 3 point cell, and a 9 point is super easy to make.
Depending on where you live, the plate vs pyrex may be a factor in the temperature equilibrium area. Here in Florida it's not normally a factor, but if you are in an area where the outside temps are more than 10 or 15 degrees cooler than your telescope storage area, it will take the plate longer to reach an acceptable level of equilibrium and give good images. Many years ago in Maryland, out club had a 14" scope made from a porthole, and during the winter we had to leave the tailgate open on the dob mount to allow the mirror to cool for at least an hour. However, once it had cooled, the images were fantastic. Nowdays, with cooling fans, etc, this is not as big a problem as back then. I still think plate is fine for most uses, especially when the price is so right!!!