Blairito,
See attached file picture, copied from Model 029 OM manual.
On the Model 029 that I overhauled the owner had the winter/ summer cover incorrectly installed, so when your all done rebuilding, check that the summer/ winter cover is installed correctly.
When I tried to figure out how to install this "L" shaped cover, it looked like the diagram in the picture but something was definitely wrong and would not work as described in the owners manual. The "L" shaped cover with a sun symbol on one side (summer use) and a snow flake on the other side (Winter use), the owner had the "L" facing towards the air filter, this is wrong. This prefilter with plastic screen hanging over the air filter would do absolutely nothing, However If you tried to turn it around (180 degrees) the "L" shape piece will not allow the top cover to go back on the chainsaw. This was a factory mistake and plastic molding problem. The Original owner, never knew there was a summer/ winter cover, and also never knew it was incorrectly installed, and the Stihl factory probably never knew of the mistake either, but Not sure How many Stihl 029's were made incorrectly this way.
So here is the fix which is very simple, I wish I had taken a photograph of my friends chainsaw after I reversed the winter/ summer cover and made the fix because the picture makes so much more sense. Any how, turn the Winter/ summer cover around 180 degrees, so that the "L" is pointing toward the spark plug, it does not matter which side is facing up winter or summer, but obviously in the winter the snow flake is up, and in the summer the sun symbol is up. Next see if your top cover will fit onto the saw correctly or if it is now hitting the winter/summer cover. If it fits correctly than you don't have a problem on your Model 029, but If the top cover hits then remove the top cover and look at how the winter/ summer cover fits down onto the inner housing and you will see that it hits an orange column of plastic, on each side, if you nip away this orange column of plastic equal distant on each side, ( I used my dremel tool but a razor knife would work too) and remove the small 1/8' diameter column of plastic, just a 1/4" or so deep. The winter/ summer cover will now press down flush into this recess, and is now installed the way it really is suppose to be.
I know this sounds a little confusing, and its hard to believe that Stihl didn't realize this mistake but then my friend that owned the chainsaw didn't realize there was even a winter summer cover in his chain saw. Lol, If my description still doesn't help, I may be able to get to my friends home sometime and take a few pictures, and you will see exactly what I'm talking about.