Hi Klaus,

Agree with all John has said. A tip I would provide is: If you are building a zenith with pulled rivets you will become a pro at taking them out. Sacrifice a few rivets (you don't need many) to hold the skin you will have to open for inspection rather than using clecos. Clecos make it hard to store parts, and over time with moving parts around catch on stuff and damage the cleco and more importantly the hole they are in. 

Re rivet removal:

Get a good Starrett automatic punch, hit the mandrel a couple of times to drive it away from the shop head, drill off the shop head using size for size bit and set the drill aside. Then hit the mandrel with the punch again it will likely fly clear first time unless the rivet is into a spar or something thicker, then you will have to hit it a few more times. Counter intuitively A5's are easier to remove than A4's as the punch can get a bit deeper in the A5 rivet. Unless something really goes sideways you should be able to avoid using the drill to knock off he shop head.

Thank you Perry and John. I will folow your advise. I was wondering if i have to buy more clecos. Klaus.

Perry made a very pertinent comment about how easy the blind rivets are to drill out. Build things like your stab but only use a few pulled rivets to stabilize the parts and close the top.  Saves cleos and MUCH easier to store the component.  THen, just drill those few rivets out bewore you inspector comes for the pre-cover.

In fact I have a friend who built an RV who  decided to just use pulled rivets instead of installing nutplates for a couple of cockpit inspection panels.  tHe odd time he wants to check his fuel fittings he just drills them out. And you know how anal RV builders can be!  ;)  {poke poke}