I found this topic very interesting, so I spent a few hours
on that.

You may try my phaserTarget demo, download it under my sig.
One important thing is the phaser model, you need to position
it well in MED in order to let it scale probably in game,
I think you've already know it.

If you want to use your own phaser, you may follow my setting
in MED :

MED->File->Preference->Video Out :

Check 2d Grid, Grid Lo = 1.00, Grid Hi = 4.

Load the phaser.mdl, on Topview, zoom in very very close
and see how I position and scale the vertices at the
worldposition centre and its size.

Hope this helps.