I'm interested in trying tube rolling; however, after removing the 6 top screws and the 4 side screws off the top cover, the cover still seems to be suck on. What's the next step that I need to do? Thanks.
I have a T8, not an Avastar, but I'm guessing they are similar.
If you have removed four side screws, you have two more to go - one on each side.
Look on the sides; just under the seam between the top cover and the bottom, right in the very center, there is one screw on each side. Remove those, and you'll be rollin'.

Have fun,
Jerry