Zantozzzz

I have a Catalyst 100 and play mostly metal. I am told having a closed back is preferred for metal amps. Would it be okay if I used a piece of plywood to close the back of the amp? Also, would it be worth upgrading the speaker to a Celestion V30 as long as it has the same Ohms and Watts?

I just tried to download Catalyst Edit from Google Play but it says I am unable to due to my Android version being too new for the app. I can still use it on my computer but I would love to use my tablet for it.