I'm 6'2 and ride an XL hardtail. I found a killer deal for a full suspension that is a Large frame. Since I am basically right in the middle of large and xl frames would it work riding a large?
I'm tall but not a big guy
Each manufacturer sets its' own guidelines for frame sizing based on their frame geometry. The only true way to judge what size frame you need is to ride the bike and see if it is comfortable. Don't buy if you can't ride it. Since frames are sized by more than one means of measurement there is no true standard. Some makers use small, med, large others are numerically odd numbers and others are numerically even numbers. You might fit on one type of frame and the same size from a different company could be too large or too small. If you want to complicate things add in different wheel sizes 26"vs 27.5 vs 29er and it gets even more confusing.
From one tall guy (I'm 6'3") to another, I can say it's really down to riding style and feel. I prefer my XC hardtail to be a bit longer and taller so I can maximize my power size of my body. However, I did the same thing when I bought my full-suspension bike, I went a size down from XL to L. I really enjoy how easy it is to get my weight over the back of the bike and how playful a smaller frame can be.
To some degree you can adjust the fit with parts choices as well. Adding a set-back seatpost and a longer stem will stretch out your body position for instance. Running longer cranks can help with a slightly shorter seattube length. Of course, this might also change the bike's handling characteristics, but at least it's easier to change crank arms than a frame!
Now, if you ride it, or try a similarly sized bike and it's not comfortable, I wouldn't force it. There's always more bikes for sale and having one that fits you is way more important than saving a few bucks now.