Hey Laser, the arrow cluster is an island all its own. If you want hardcore row regularity right across the board, well, SA is not complete enough for you. Up arrow would be R4 while the other arrows would be R3. But our available SHIFTs are either R3, or an imperfect R4:
That's Round 4 SPH as it is now, with imperfectly fitting row 3 mods all round, until 7bit ships the all new right fitting R3 mods.
So there's a good case for R3 for all arrows, as good fitting mods will be those, on both the bottom rows of the keyboard.