Wheel spacer question

I called a place that said they could do what ever thickness and what ever bolt pattern i need. I am not sure how thick i need it to be and i dont want to throw 50 bucks away on a guess. was thinking i could have a friends machine me a set and check it. too thick cut it until it fits right measure it and then order my set at that thickness.........sound right? just need a starting point. they said they can make them up to 2.3 inches thick.....