Hi rob,

Nice to see you back again thou would nicer still to see pics of a welded frame so get the welder fired up and lets see some action. . Lol

Don't worry too much about only being 3mm it still taps and holds threads with smaller bolt sizes. If you need larger bolts in places you can't reach back of then there's other quick and dirty ways like drilling larger hole and inserting a nut weld in place and grind flat.

So now go away and don't come back without pics of a welded frame. .