I would say a certain amount of precision is required. Otherwise you could end up with the holes in different spots on the left and right side. Then your wheels would stick out different amounts from the center of the car, or you would end up with different length control arms to compensate. The set I got had multiple holes and could be flipped forwards or backwards. Giving you
like 6 11 different positions to lock your lower control arms into. I think that is part of why they cost what they cost.
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When I put my front suspension together and dialed it in, I was measuring things with thousandths of an inch. For people who are putting that much care into their steering and suspension travel probably do care about the precision. But there are tons of people out there just assembling parts together like legos and letting it be how its gonna be. For those guys, I agree, no great precision is needed.
If you didn't need any great level of flexibility or precision, I would think you could pick up a piece of bar steel from home depot. Cut it into a few sections. Stack them up together and tack weld them. Then drill a hole through all of them and whittle them down to size with an angle grinder all at once. Make sure the hole is as close to the size of your bolt as possible, or the bolt will flop around in the hole and defeat the whole purpose. I bet you could knock out a basic set of these for $15 including the steel and fasteners and an hour of your time.