So to drop devices, you have to first drop the DB.
So before do anything, i advise you to make a dump of the tb, and save the current devices setting present for that db - sp_helpdb "name"
So if you have to rollback your action, everything can be like before.
Now you can't use dump and load, because to load the db size has to be the same or higher.
So you options are:
1- Bcp out the tables.
You bulk copy out the tables then "drop database" , "sp_dropdevices" and drop the devices that you want to drop. And after recreate the db with the size you want, and bcp in the tables.
2- Create a new db on the server, with the size you desire, copy table data from one db to another, drop the old one, and rename (sp_renamedb) the new to the old name.
Hope it helps