VOC- 41.5V x 12S = 498VOC, but you have to add an additional 25% for cold condition overvoltage (unless OP is somewhere that he won't ever see 40F or colder). 498 x 1.25 = 622.5VOC. I would definitely not do more than 9 or absolute max 10 panels in series on this voltage rated mppt!Instead of 3x 8S strings set your panels to 2 strings of 12 panels. Still within 18K voltage limits and you have the input 1 mppt free for future use?
Hitting that voltage level (600+ volts) even once will very likely destroy the mppts!