I have carried a lot with one and highly recommend a very safe handgun with a long hard first trigger pull and/or a very good safety,,,I carried a Walther PPK.
The holster in front goes between your underwear and your pants with your shirt tucked underneath the holster,,, in back tuck your shirt over the waist band as it can ride up and show above your pants. The handle of the gun can print wear loose or pleated pants.
Actually Smartcarry is a knock off of Thunderwear,,,I was working on a similar holster when I saw an ad in a magazine for one so I called Tom in Satellite Beach, Florida,,,he had the patent and contracted a local swimwear factory to make the holsters for him,,,he collected the orders and the money had the holsters made paid the company and shipped them out to his customers. His ex friend Charlie took his patent and eliminated the ribbon strap across the top seam of the holster claiming the gun would snag there and patented his Smartcarry holster same holster just minus one top ribbon strap over the top seam of holster.
This is perfectly legal by the way,,,if you patent anything make it as simple or stripped down as possible,,,someone else can take your idea and add to it which is not legal,,,but if they subtract or delete from it,,, that is legal to patent.
For years Tom did all the magazine advertising but Charlie was much better on the internet and then Tom sold his company to relatives and now I believe Smartcarry has the most sales. An interesting holster system I own two or three in my huge box of different holsters I have tried over the years.