I don't mind using side arms for roostering out or extending away from but not on a horizontal plane from a vertical pipe. Believe that's not what they are designed for doing or a good idea.
Normal side arms have C-Clamps on them the same as fixtures but as opposed to fixture clamped directly to the boom, these fixtures attached to a side arm have much more torque going against and possibly over-stressing the clamp. Given the sea changer is more heavy than a normal
Leko, I would be concerned for two reasons. First if your side arm is the normal ½" sch. 40 normal water pipe instead of sch. 80 water pipe, that pipe could bend. Second and more important the side arm could fail more easy in a direct proportion of side arm length to the amount of extra torque that side arm is putting on the C-Clamp - in direct relation to that.
There is some old style side arms out there that have a bit more reinforcement to the clamp portion but if it’s the normal side arm that’s just a
Altman clamp with cotter pin pipe in it, I would be concerned about the added torque over what weight is normally known for such a thing. (Again a Sch. 80 pipe is recommended.)
A better way to side arm for these lights would be to do cheseboroughs with the desired length of
batten pipe or 1.1/2" Sch. 40 pipe to the boom. The cheseborough is rated for much more weight. Another option is to use ½ cheseboroughs welded to 2" aluminum pipe, or RotaLocks which are similar to cheseboroughs but not really as good for this type of application.
As always,
safety cable each fixture not to the side arm but to the boom. A double wrapped
sunday loop or Perstrusk (sp) Knot of wire rope to the boom so it cannot slide down the boom with the safety cable hooked or looped to it is possibly the best way to do this.
I have also seen safety cables latched to eyelet rigged ½ cheseboroughs or at times C-Clamps that don’t have fixtures on them also.