Problems with str8 stems

Recently I've being doing a bar conversion for my zip, Ive got some pro tapers and a str8 stem.
when tightening the top bolts so my bars didn't move back and forth they got fairly tight but my bars still moved a bit, so I tightened them a bit more and it stripped the thread so I had to buy another, as I was putting the second one on the bars weren't even tight on the stem and I could still easily move them back and forth and the thread stripped before the bolt even got tight so now I'm stuck with two stems both stripped thread but I'm going to see if I can get them tapped and re threaded.
Another problem I had were the stem doesn't actually sit over the fork it just sits on top so when tightened up the stem still has "play" side to side

Anyone else had problems like this with there str8 stems or on there zips?

Does anyone recommend a good quality stem that will fit my zip sp?

EXACTLY the same problem and mine can spin around in the steer tube no matter how tight i do it up, any idea?

Never had that problem on the Ovetto. Are you sure it's the right stem for the Zip/Peugeot ? Otherwise - it's time to make a shim from a coke can..... I did have the problem with the Stage6 stem - but I solved this with a big/straight M6 bolt & nut that goes in one side & out the other. I had to dremel a flat surface on one side - but it works.