What makes SP so different?

I've always considered Street Pro to be a tuners class. The build isn't that unique. Street Stock is very similar.
Wheel prep is no different than Basx or Street Stock. Same can be said of axle prep.

What can make the SP class more difficult is the light wheels. The side wall flex is a variable that is not present in other classes.
This flex will put a premium on the drill of the car and your ability to tune the car. It is definitely a challenge to find the sweet spot where the speed just flows out of the car. It's the challenge that makes the class so much fun.

Because it's the only fat wheel that is light. Any mistakes in the build are accentuated. It requires a tight build, tolerance wise. It's easy to say it's not that hard because of experience and it's really not. It's a class where your technique will shine. I would say it's as meticulous as Unlimited but you have to add in the prep. It used to be my favorite class. Once the wheel shields got added it added more to the equation.

Mojo was running new style wheels this month.

Thanks for all the responses! Who says NPWDRL isn't full of people willing to help? Ask and ye shall receive!

Agree with everything mentioned above. For me, it's not the build itself but rather the tuning. As Brian mentioned, it's finding that sweet spot. Those wheels are not forgiving at all if I'm not dead on with the tune. Even when I find it, it is difficult to repeat it between re-preps. I find the wheels not only to be more suseptable to dings and hairline cracks but very sensitive performance wise to those dings and cracks. It's a tuners nightmare for me but when that elusive sweet spot is found, all the extra time spent chasing it seems justified. I seem to have more luck with the sweet spot on new builds so I built a new SP for finals. We'll see if my luck continues. Highly recommend having extra wheels though, especially if the groom on your test track is less than perfect.