50mm seems odd to me as well considering Clough32 says it should be something like 27 on the Itty Bitty Flex Dual Extruder... BUT when I measured it said 50 on the nose.

I switched my settings back to mostly the same after finding the offsets in the configuration_adv.h:

Still using this bit:

Code:
#define X_PROBE_OFFSET_FROM_EXTRUDER 50  // X offset: -left  +right  [of the nozzle]
#define Y_PROBE_OFFSET_FROM_EXTRUDER -5  // Y offset: -front +behind [the nozzle]
#define Z_PROBE_OFFSET_FROM_EXTRUDER -0.65   // Z offset: -below +above  [the nozzle]
Changed this back to the 3 points that are just barely inside the range:

Code:
 //===========================================================================
  //========================= Unified Bed Leveling ============================
  //===========================================================================


  #define UBL_MESH_INSET 1          // Mesh inset margin on print area
  #define GRID_MAX_POINTS_X 10      // Don't use more than 15 points per axis, implementation limited.
  #define GRID_MAX_POINTS_Y GRID_MAX_POINTS_X
  #define UBL_PROBE_PT_1_X 55       // These set the probe locations for when UBL does a 3-Point leveling
  #define UBL_PROBE_PT_1_Y 180      // of the mesh.
  #define UBL_PROBE_PT_2_X 55
  #define UBL_PROBE_PT_2_Y 20
  #define UBL_PROBE_PT_3_X 180
  #define UBL_PROBE_PT_3_Y 20
  #define UBL_G26_MESH_EDITING    // Enable G26 mesh editing


#elif ENABLED(MESH_BED_LEVELING)
And then changed on the advanced page:

Code:
  #define UBL_MESH_MIN_X (X_MIN_POS + (UBL_MESH_INSET + 10))
  #define UBL_MESH_MAX_X (X_MAX_POS - ((UBL_MESH_INSET - 10)))



Using this setup I ran the G29 P1 (and subsequently G29 T) to get this map:

Bed Topography Report:
(0,9) (9,9)
(11,309) (309,309)
. . . . . . . . . .


. . 0.360 0.262 0.132 0.038 -0.118 -0.242 -0.430 .


. . 0.352 0.248 0.105 -0.020 -0.170 -0.317 -0.538 .


. . 0.360 0.240 0.080 -0.077 -0.247 -0.407 -0.607 .


. . 0.428 [ 0.230] 0.067 -0.102 -0.287 -0.477 -0.713 .


. . 0.357 0.200 0.045 -0.130 -0.327 -0.518 -0.740 .


. . 0.367 0.225 0.040 -0.145 -0.345 -0.550 -0.810 .


. . 0.367 0.212 0.020 -0.165 -0.402 -0.615 -0.865 .


. . 0.395 0.202 -0.002 -0.212 -0.415 -0.667 -0.930 .


. . 0.390 0.197 -0.030 -0.220 -0.495 -0.740 -1.027 .
(11,1) (309,1)
(0,0) (9,0)