To my way of thinking, you cannot do a barrel roll at 1g. Firstly, you have to pull the nose up to start it. That's more than 1g. Secondly, you have to pull more than 1g to get the nose back up to the horizon again after being inverted, unless you do a wiffodil and twinkle roll to wings-level at the end, but then you'd end up at a higher altitude than when you started.
It would be quite easy to do in a big jet at less than 2g provided you don't let the nose get too low after inverted and have to pull like a $%^&*@ to recover; start nose-high and keep the roll-rate up ie don't do it the way Tex did it. Start rolling with the nose well up.