You have about 1cm between the mounting plate and the fins to glue your sinks. Also, the heatpipes' slope adds a bit to the width of the plate so make sure there are no ~5mm and higher components on a roughly 6.5x8cm rectangle centered on the chip.
Arctic provide detailed drawings of this cooler on their site: https://www.arctic.ac/ch_en...
I used a bunch of 20x5mm sinks on my card to be sure, but I would've been fine with 8-9mm.
My biggest problem with the cooler was the sink that goes on the other side of the card, since my motherboard had components in the way (suspected as much before buying the cooler, but it was a bummer anyway...).
Have fun putting this together :)