This plane has the velcro in it for thr radio gear right? I wouldn't move the radio gear, because that velcro very easily saves your airplane and i have seen it happen.
A friend of mine has a cub and theres wasn't strapped down, they did a loop and they were in that loop for about 15-20 full loops till it augered the ground.

The reciver pack came undone in the high g's. So just put some weight in a little at a time. and nose should be slightly down, yet hardly noticeable