Rudder "Oil Can" noise

I posted this question on another site and got a few replies, no help really. I was wondering if anyone over here could help. I am nearing completion of the rudder on my RV7A to the point of the dreaded training edge. I have been following Van's recommendation and clecoed the trailing edge to a rigid, straight piece of aluminum angle. Next, I will use fuel tank selant to bond the T edge before setting the rivets. The edge is nice and straight now. However, I noticed the skin makes a poping noise when I press on it, kinda like an old oil can, between stiffeners 915D and 915E on the left side and between stiffeners 915A and 915B on the right side. The rest of the skin between the stiffeners is nice and tight. Is this a problem? If this is a problem, how can it be fixed?
Thanks for your comments / suggestions.
Wes

Oil canning rudder

No, it's not a problem. Those new rudder skins are so thin that they will do that. My rudder on my -7 does that, and in flight, although I don't hear anything, I've had people flying my wing say they can see it oil canning a bit in the sunlight. Again, normal for something so thin.

I would say (keep in mind, I am an idiot and you get what you pay for) the oil canning isn't a problem. Pretty much, what he said.

One more thing to add though:

Watch for cracks in the aluminum. Check around rivets, at folds and along stiffeners at intervals. If a crack is noticed, stop drill it and put a new rudder on the list of things to do.

...just what I would do.

CJ

Back when I built the rudder for my -9 I missed cutting the angle at the end of my stiffeners and they interfered with the spar when I tried to close it up. (I had to drill off one of the skins, trim the stiffeners, and put it back together.)

Check your stiffeners, you might have missed one.

As for riveting the trailing edge. Check the aileron section of my web site for a picture of the rivet set I ground down to squeeze these rivets. It worked much better than driving them. Also, I found it much better to put a cleco in every hole but alternating sides. This will keep those trailing edges straight while the proseal dries.

Just my $.02.