Doing full screen is really a big issue in Classic, so I'm still curious how to do it without all the negative ramifications myself. There are ways, but each of them has their own big drawbacks.
Here's a method I've been using: http://www.scirra.com/forum/topic47220_post295684.html
However, if your layout is a certain size, for me at least, my sprites get all messed up. I asked TL22 (The creator of the example) today if he can help, so I'm hoping he knows of a fix.
The other one I know of is Ashley's example:
The issue here is that there are little kinks in the system when using this. I'd rather not bother with it because you aren't allowed to use 0% scroll rates, meaning you can't use layers for pausing and a HUD etc. etc.
The actual fullscreen feature of Classic simply doesn't work. I really hope it's fixed some day. =/