How to lash a ring to a spar

[whimsy]

I'm junk rigging Flutterby right now, and having trouble with my yards.

I need to attach two blocks to each yard, one for the halyard (3:1 purchase), going UP, and one for the yard hauling parrel (simple block, pulling at 90 degrees to the halyard. In normal use, the yard itself is at 50 or 60 degrees from horizontal. The "conventional" solutions involve hardware bolted to a (wooden) yard. I don't want to drill holes, or weld anything if I can do what I want securely using rope.

My yard is an aluminum pole (2.3 inch outside diameter) I've got a 2 inch diameter SS ring. I'm thinking to try lashing it to the yard so that the open axis is perpendicular to the axis of the spar like this:

______O______
----------------------

I would then use normal SS shackles to attach both blocks to the ring.

Now I'm trying to decide how to tie it on. A round lashing looks like a possibility. A shear lashing (with frapping turns) looks better.

My halyard is 3/8" polyester braid. Since it is a 3:1 purchase, to approximately match the strength I would want at least three turns of this size rope. Four turns through the ring is the absolute maximum before it rides too far up the sides. If I wanted more turns (looks normal for this sort of lashing), I'd have to go to something smaller. I've got 1/4" polyester line and 1/8" cord I could use instead.

Does the lashing sound secure? Would something else work better?