1. I don't think you'll have to worry too much about having to tune them much after you get it to where you like it. Initially you'll have to have a friend or mirror handy to get it to adjust, but once you do, I don't see it moving on it's own. Unless they are broken and/or loose and adjust on their own, you don't need to secure them.
2. You should have an access panel on the back of your cab regardless. It makes life much easier for smaller repairs. If you've already covered it, cut out a large rectangular hole, then make a "door" for it with a latch or some key-entry method. I mean, if you've got it all covered up, you can do without it - but it'll make little problems take longer to fix.