aside from bondo not holding well on aluminum, the aluminum is waaay flexible, and the slightest bump on it will flex the bondo off - in addition there may be some reaction between the aluminum and the steel it's against, and if he left any rust under there it'll be bubbling and flaking soon
what they used 'in the day' was any scrap metal layin around pop riveted on - or easier, some fiberglas fly screen w/ a good coat of bondo mushed into it - last longer than aluminum I'd think!
st least he told ya about it, but unless yer into redoin the bodywork before you paint it, I'd pass
Bill
