FWIW, my 11x14 Cescolite measures 15.5 x 18.5 (inches). So add at least 4.5 inches to your 30x40. The interior dimension at the base, before the edge starts curving up, is 11x14.

Mine is many years old (not sure how old) and I didn't see a model number on mine (just says "11x14"). So current models might be different.