That's human nature for you! The fact that folks appear to be asking for slotting of an OE part rather than, say, bushings like what was done up front is the surprising part to me. The only reason the slotting was done on Steyn's car in the first place was in hopes that it wouldn't be caught. If we are looking to change a rule for the same end result as what those slots did, I would prefere the rule be written to use the correct part(s) instead of modifying an OE part.
That said, I'm not sure if I support the change at all or not....still building my car and have not checked alignment yet
In addition to the obvious advantage of being able to obtain more camber there are other aspects that were considered;
- Cost- about as cheap a modification as can be found.
- Difficulty - can be performed on or off the car with simple tools from a rat-tailed file to a simple die grinder (just be careful not to exceed the allowance given as calipers with resolution 0.001 inch will be the inspection tool of choice).
- Time - Should not take much discussion to haggle on the labor charges involved if you elect not to do it yourself.
- Investment and obsolescence- no need to buy additional arms, use what you have.
- Due to the variation in how much camber some vehicles are able to obtain, it either becomes necessary to swap out any number of parts to find the actual culprit part(s). As we all know this can be time consuming and expensive depending on your resources and/or abilities.
- In lieu of the parts swapping routine or in the event an adequate solution is not found, the most probable solution would be to apply a porta-power to the bottom of the cradle to spread it to obtain desired camber. The issue with this is that you are now effectively increasing the track width of the vehicle, which of itself could create an additional competitive advantage. Slotting the upper arm does the opposite effectively reducing track width.
- Requiring use of offset bushings in the upper rear arms introduces additional cost and installation expense as well as introducing the potential for variation in orientation between each offset bushing (not a significant issue in and of itself) but it does make for a difficult/time consuming process to change bushing orientation for purposes of camber adjustments.
- A primary advantage for slotting the upper rear arm outer hole is that it allows a quick and easy way to introduce additional rear camber WITHOUT affecting the rear toe setting. This allows those who want the ability to evaluate "at the track" camber changes the ability to do so without having to deal with chasing the two lower rear control arm cam bolt settings while in the process not screwing up the rear toe setting. This is really throwing a bone to all of the DIY low buck competitors that do not have large support crews and equipment at their beck and call with the ability to make this evaluation and if necessary get back to where they were, if so desired.
My opinion is that this is a decision based in common sense that does not favor or advantage any competitor over another but rather codifies something that is simple cheap and useful.