It's generally a bad idea to have it that close IME. Fairly easy to flex even the most rigid rails to impinge on the barrel, like loading a bipod etc, not to mention if you try and use a mounting slot if its keymod or mlok. Other than that, as long as there isn't any other factor dicking with your harmonics, it's not inherently bad to have a suppressor "reflexed" into the handguard. It'll also get that handguard nice and hot real fast too if it's not like carbon fiber or something.
Generally speaking, I don't think there would be enough whip to cause the barrel to impact the handguard and the bullet would be out the barrel anyway. Especially in anything heavier than a LW profile barrel.
Get a wider handguard if that's what you want to do would be my suggestion, a little more forgiving.