I have changed to the ULCS 8 inch double bouyancy arms and they worked perfectly. I have the big 110 lens and lights, so it's all fairly heavy underwater.
These work out about the same length as the Locline arms. Still not enough to make it just slightly negative (as I would prefer it) but it's on the right track. I am looking at either PVC pipe sealed at each end, or foam to add a bit more bouyancy for next time out.
But the ULCS arms are very stable, lock perfectly, and they allow easy movement without altering the clamps at all. I just set it to the right tension at the start of the dive, and just move to the right position as needed.
If you can fit them in your case for travel, you could go to the 10 inch version, these give quite a bit more buoyancy and aren't too long.
I probably wouldn't go longer than that, no need really.