I picked up a new Viper PST 6-24x50 and have it sighted in. I'm confused about the spacers for the turrets. If I put them in will it keep the turrets from going all the way down? There isn't much uptravel left for dialing in for distance.

Zero the scope at 100 yards. Remove the turret, slide the shims in, and keep adding as tight as you can get them alternating the openings. Once you have the gap filled up with shims reinstall the turret with zero on the turret matching zero on the scope body. Now you can dial impact "up" all you want, but you cannot dial below your zero, the turret will stop just below your zero, probably less than 1.0 Mil. That is a zero stop turret.

If there isn't much elevation left, then you've got another problem. You'll need a canted base, say 20 MOA (can also be done, less ideally with Burris Signature rings). That 20 MOA will give you back what you need. I had no problems with the Viper PST and elevation when I was running it on my 6XC, but mileage varies. If you've got more drop, then you might run out.

I had the opposite of the OP.

With a 20 moa base it was way hi with elevation down maxed out. Had to put a 0-MOA base and use Burris Z-rings for an effective negative 10-MOA to get it sited in. When I set the zero stop I was only able to fit "1" shim in so I have approximately 75-80 MOA of come up.

Sounds like you need a 20-MOA base or similar. I have a EGW silver one for a savage short action round receiver if you are interested.

I have the EGW 20 Moa base, I would like shorter rings as I'm using 1 inch tall rings right now. So if I have to dial for shooting angles down/up which both will hit high if not dialed, then using the shims I won't be able to dial down, correct? Same for dialing windage?

With a 100 yard zero you will NEVER need to dial down, only up. With the shims your turret will stop at the 100 yard zero.

Windage doesn't get shims. You can dial wind as needed, but still zero the windage turret.