Compare the top plate to the large top plate that comes with the Kanto and the dimensions of the hole locations on the R3. It works with the Kanto large top plate , so if the top plate is as big or bigger than that it will work. Will likely require drilling or modifying holes.
Simply by looking at mounting plate sizes, the SX26 is 16.5 cm x 23.5 cm which means that presumably the much cheaper Stylum 2 at 165 x 220 mm would also work.
I need to look below the R3 and measure the mounting hole spacing - looks like there is no drawing of that anywhere.