Pontiac G8 2008-2010 - Help Please - Installed the UDP, but the belts were a problem...

So I ordered an SLP UDP. Marylandspeed and just about every other website that sells them lists the belts needed as

Pontiac G8/GXP
Main Belt: 6PK1880 or Equivalent
Accessory Belt: 4PK1080 or Equivalent

So I ordered all the belts ahead of time. I get my UDP and belts in the mail and the instructions for the pulley says the belts are

Pontiac G8
Main Belt: 6pk1860 or Equivalent
Accessory Belt: 4PK1050 or Equivalent

First the accessory belt I ordered wan't even close to fitting and sagged bad lol. Had to go to a part store and closest belt I could find to fit was a 4PK1054. Seemed to be spot on.
The Main belt I bought based on what Maryland speed posted is about one inch smaller than the one listed in SLP's instructions that came in the pulley box.

I installed the belt marylandspeed said anyway and it seemed to work fine, but I don't know if having a belt that is possibly too small will cause issues, and what warning signs should I look for?

I haven't retuned the car because I heard it wasn't neccisary, but occasionally it bogs for a second if I quickly jump on the gas since the install. Also my lights do visibly dim at idle although I heard that this is not an issue on the G8. I can see the lights brighten as I go from idle to just a slight bit of gas. My atari battery indicator only drops a single bar occasionally. Some times it drops to halfway if I am sitting in really awful traffic.

Thanks for any and all feed back!

If the belt is to small starting can be somewhat labored. You should have just a little bit of give in your belts

It would have ot be really small to cause any real issues. Other than that you are good, when you have the car tuned have them increase the idle speed just a bit and it will help with the dim lights and bogging.

I have had a UDP on my GXP since 500 miles on the clock with no issues.

Thanks for the info guys. I'm going to stop worrying about it now...

Still have issues with the accessories?