Backspace on Magnum Drag 2.0

[TurboBuick]

Hi, I need to know how the backspace is measured by Weld Racing on the Magnum Drag wheels. Is it measured to the very outer lip/edge of the rim or is it measured to the lip of the rim?

Basically should I lay the flat edge on the outer lip, or should I lay the flat edge on the inner lip? There is a 1/4" difference depending on where you you measure to, and I would really like to know how Weld measures this.

Thanks.

[Weld 3]

You always measure backspace from the very back edge of the rim lip. Lay the wheel face down and put a straight edge across the very back lip and measure from there to the mounting surface. Back space has to take into consideration the entire lip so fitment issues will be known.
Thanks