We recently purchased a size medium for my 2 year old Vizsla(Mary Jane) and a size small for my 3 year old Brittany(Denver.) Jane is slender and the medium was too big but the small worked great on both her and Denver. We gave the vest to Janes mom, my brothers dog Sioux, as she is "rounder" and it worked fantastic!
The next day we placed an order for 2 more small sized vests, 1 for the other of my dogs and 1 for my brothers other Vizsla, Janes sister Yoda.
We hunt corn, beans, hay, grass, swamps, drainage ditches, and just about any other place a bird can hide...no issues with the vests what so ever! We love the protection the vests provide and the visibiltiy! Not to mention how sharp they look on top of that. Ive hunted with skid plates and other vests in the past, while they work and are very suitable, the CUGA vest is where its at!
We spent a lot of time debating which vest to get (months) and with very little outside input we took a chance, turned out to be worth every penny for the protection the vest affords!!!
Hopefully this review helps with your decision to purchase the beat vest out on the market :)

Super. Strong strong strong. Velcro holds beyond belief. Can lift my 60 pound lab into the truck and it does not tear away. Love it.