What is the nature of the repair and grade of aluminium alloy the frame is made from? If it's a heat-treated alloy like most 6000-series then any weld-repair will result in localised changes to the metallurgic properties which can weaken the frame. 7000-series is easier to weld repair - you might get more joy from a call a few non-ferrous fabricators - but they'll likely not take liability for blowing a hole in the thin tubes.