Here's my general 2+1 set up. The side fins are bigger, and back fin an inch or two smaller than the Widow Maker. I originally tried two of Andrew Kidmans' Parmenter Widows bout 10 years ago, which was documented in his early 2000's movie Glass Love, one 6'4 and the other 6'6 ( filmed in perfect 4-6ft supa bank). They felt great in waves above 3ft but the back fin seemed to drag in smaller and lower quality conditions.
So after much trial and error, surfing and sanding, I came to a great balance with these fins, scaling thrusters up and single fins down, moving forward and back. Placed at 6 1/4 and 12 1/2 , I surf this 2+1 most days on the East Coast of Oz ( apart from the Quartets now) and they love ALL conditions from 1-2 ft beachies to cyclone season. Also a couple of seasons in Hawaii, with memorable sessions at Haleiwa and maxing Sunset.
They get away much faster than Thrusters, due to their forward placement but are drivier cause of the larger back fin, plus looser and smoother from the cluster. I do not condemn the Thruster set up in any way, or "truster" it has stabilized surfing and givin a great bench-mark to move on. I may go back there one day.