The code by ahunter is still the fastest:

   chromatic "52" : 27 secs (25.76 usr  0.04 sys = 25.80 cpu)
NoGrooTwo+ahunter : 17 secs (16.72 usr  0.04 sys = 16.76 cpu)
          japhy 1 : 16 secs (13.84 usr  0.04 sys = 13.88 cpu)
          japhy 2 : 12 secs (11.71 usr  0.07 sys = 11.78 cpu)
          ahunter :  5 secs ( 4.65 usr  0.00 sys =  4.65 cpu)
 ahunter+turnstep :  3 secs ( 3.62 usr  0.03 sys =  3.65 cpu)
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