MrV, before deciding if you would consider me a "professional sports bettor," which is largely a matter of counts and amounts and opinions, check out the posted tickets in the Retro Road Trip thread and decide if those amounts constitute "professionalism." Some posters are very, shall we say, selective in what data they include in their posts (when they're not being caught in innumerable lies).
For example, both the KewlJ(s) and myself have accounts at Oddsmaker.ag. I have a dozen or so offshore accounts, and Oddsmaker would be considered a "boutique" sportsbook (not a big one). Now my wagering there totals somewhere between half a million and a million. Is that indicative of "professionalism?" I have no idea; you'll have to ask the Kewj(s). Maybe they've bet more there; I have no idea.