Thanks for letting me test these beasts. Can't wait to spend hours and hours skating these.
Saved or downloaded, they take the same amount of space. The only way to really add space is to either upload them privately for yourself and download them again later, or leave them bookmarked and do the same. You'll need to re-download, but it's as close as you can get to "Cloud" storage.
Or create a new gamertag and switch back and forth. 100 new park slots right there.