By one pin shooting i mean slideing sights. If a deer is between 20 and 25 showd I use the closest or put in the middle. Thanks.

With modern bows and arrow speeds as they are, I don't think it will matter more than an inch at best.
Practice at 20 and 25 yrds with the slide set to both 20 and 25 yrds. I'll bet there isn't enough difference to worry about, like I said, probably not more than an inch.
I don't have a 20 yrd pin. I have 25, 35, and 45 yard pins. In reality, I could use my 35 yrd pin and simply hit slightly high at anything under and slightly low out to 40 or so.
I have actually considered removing all pins except one set at 30 yards.
The main reason I haven't is that most deer I've shot were 10-15 yards, and I don't want to hit too high.

Ever consider a pendulum,Cabelas has a great one made by Keller,89 bucks

I think you're talking about "pin gap shooting" If you have a 20, 25, 30 yard pins and the deer is at 22.5 yard then you put the 20 yard pin above and the 25 yard below.

One pin shooting is really having only one pin. Most hunters sight it in at 20 or 25 yards. When practicing, they learn how high or low to aim depending how close or far the target is from 20 or 25 yards. this method is very good for faster set-ups. For slower set-up multiple pins are usually better. Example - 10, 20, 30 to your max.

Hope tis helps....Good Luck!