[racket] help packaging .plt file

Hi,

I am creating a small plugin for the first time. 

I create the .plt file using: raco planet create mydir/

While "it works", I get some problems with installation:

- if I install the .plt "from file", the install works but for some reason I have to manually specify the target directory (a window pops up systematically, asking for the directory). This does not happen with other .plt files I install manually. (I'm on mac os, these .plt get installed in ~/Library/Racket/5.2/collects)

- I put the .plt file on a web server and tried to install .plt "from web". In that case I get an error:
gnu-unzip: bad header

 === context ===
/Applications/@Sync/Racket/collects/mzlib/inflate.rkt:857:2: do-gunzip

not an unpackable distribution archive

 === context ===
/Applications/@Sync/Racket/collects/setup/unpack.rkt:271:7


Is there something special to specify so that the package can be installed from web, and automatically in the local collects?

Thanks in advance!

-- Éric