Roy, I almost always use OIS and I've found it to actually be better on my Z5 than my VX2100 despite the Z5's much longer reach. Try using 'hard' under the OIS settings and I think you'll be pleased. That setting gives you a 'stronger' image stabilization.

As for the shimmering, the few times I've noticed that were when I saw I was actually (unknown to me) videotaping heat shimmering. It's exactly the same effect as when you look through a telescope across an area which is warmer. I saw it with the Z5 when I was using the 20X zoom from within my house and shooting out of my open patio door on a very cold day. But I've never seen it at wide angle.

OIS Hard Setting
 

Ken,
Thanks for the tip - I'll definitely give it a try. I'm fairly certain that what I'm seeing is not shimmer caused by heat - but I'll need to experiment more with on- and off-tripod shots to be sure.
Aloha,
Roy