rashguard fit?

[JDV5811]

so i just received my new rash guard in the mail. i tried it on and its good tight fit everywhere basically but my waist. it seems a little loose and not tight around my midsection. i was wondering if you guys recommend to go down to a medium or stick with the large. im 5'9 around 158.

 

[Sobral]

we need to know your height, weight and body type (skinny, fat)