Go wing installation question for 74 Duster

Hi I just did a install on my sons 74 Duster, I bought him a go-wing and brackets from RPM restorations in Saskatoon, nice product by the way, there were no templates with the brackets and no cut outs on the trunk, we just found a picture on the web of the installed product, and basically held up the brackets and traced out the cut out and used a 4 1/2 inch angle grinder, it worked well, be careful with the cut out its tight