Newbie questions / mapExtent / missing tiles / zoom-limit

Hello,

I'm really new to modestmaps and I am having some trouble figuring pretty basic stuff out. So I was hoping, you guys could maybe answer some questions for me:

—What exactly does mapExtent do? I figured, it would set the outer boundries of my (custom) map, but that doesn't really seem to work so well.
In the sampleClient2, three locations are being passend onto the function:
container.map.setExtend([new Location(66.4994, 25.692666),
new Location(66.491170, 25.726891),
new Location(66.502030, 25.747029)]);
but I've I'm trying to use it this way inside my class, I'll get a "type-mismatch"-error.
On the opposite, if I'm using it, as suggested by the sampleClient1:
__map.setExtent(new MapExtent(37.829853, 37.700121, -122.212601, -122.514725));
the zoom-factor of my map is somehow way to low and a lot of "empty" space (—no tiles existing) besides my custom map is visible

—Something seems to limit my max zoomlevel to 6 and since I've been building my own client on top of the sampleClient1.as, I'm kinda hoping, I'd have missed some settings from the former client. My custom map-tiles should allow up to 14 zoom-levels, if I've gotten that right.
Information: Since "mapExtent" doesn't really work, I'm currently using "setCenterZoom" with a higher zoom-level to compensate

—I've been using two different custom maps so far and followed the ACtransit-tutorial to the point. The first time (map-width:10.000px->PSD-file) everything went fine, the second time (map-width:>20.000px->JPG-file) I'm missing certain parts of tile-rows in certain zoom-levels.
I initially thought, it could be a problem with the zoomifyer-app. and re-tiled the map again, but the problem remained the same

***

I know that's a lot of questions, but I'd be really greatful, if someone could help me out.
I'm trying to get to understand this great tool, but it's a bit tricky to get behind the curtain.

Thanks for all your help,
—trice