Is the Ram 111 with 1.5 in ball sufficient to hold the HB 10 up?

No, if you are gonna go with ram mount with a 10" unit you will want to use the 2.25" ball. Ram is coming out with a specific mount for the Helix units. The mounting base plate will match the holes better on the gimbal bracket

RAM Mount 2.25" Ball Mount w/3.68" Round Base & 2" x 5" Rectangular Base f/Humminbird Helix 9, 10 & 12
Model: RAM-D-202-25-C-202U
$95.49


RAM Mount 2.25" Ball Mount with 3.68" Round Base & 2" x 5" Rectangular Base f/Humminbird Helix 9, 10 & 12

The RAM-D-202-25-C-202, powder coated marine grade aluminum mount, consists of a double socket arm, one round 3.68" diameter round base and one 2" x 5" rectangular plate. The round plate contains two mounting holes at 180-degrees and three mounting holes at 120-degrees. The rectangular plate contains a 4-hole pattern of 1.5" x 4.5". The patented rubber ball and socket technology dampens shock and vibration, and allows for nearly infinite adjustability, So you can set your device at the perfect veiwing angle, while suited for any rugged environment.

Compatible Devices:
Humminbird Helix 9
Humminbird Helix 10
Humminbird Helix 12


Specifications:
Overall Length: 7.875"
Weight Capacity: Up to 15 lbs.
Weight: 3.07 lbs.