Hi Tom:
Yes, I can easily adjust the position of the battery in the "electronics bay" by making mount plates that position it fore or aft as required. Initially I make a location/mount plate that puts the CG slightly forward (Like the saying goes, a nose heavy ship will be sluggish, but a tailheavy one might not get a second flight...) of the point where I think it will ultimately reside. I can then make plates that hold the battery progressively further aft. When I find the "sweet spot," I duplicate that battery plate and mount all my batteries in that design plate.
My mount system also allows me to move the battery up or down a good bit to allow for vertical CG adjustments. This is one of the many advantages that electric has over glow.
As for the "screwless" mounting... I'm not a fan of it. I'm a belt and suspender kind of guy when it comes to mounting the battery and the battery cover (cowling or canopy...). It takes me just slightly longer to remove and install screws, but the peace of mind is more than worth it. I've seen two batteries "exit" models in mid air so far, and, thankfully neither of them exited from my airplane. Believe me, that can ruin your day. It sure did for those two electric enthusiasts. I'll bet their batteries are held in now with bolts... The worst way is with Velcro. Velcro picks up dirt, loose grass blades, etc and not only loses some of its holding power, but it also look awful. Stick to bolts, or a nut atop a threaded stud.
Later - Bob