Umm... you serious?
The chain is gonna feel loose, because it's a derailler setup... the "rear mechanism" keeps enough tension on the chain to keep it from falling off, but it has to be loose so it can change gears.
How does the "rear mechanism" (I'm assuming you mean the derailler? The thing that moves the chain onto different gears?) "get in the way a lot"? In the way of what?
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But working at a job where I can't surf BikeForums all day any more...