Messy Marv, a.k.a. The Boy Boy Young Mess, is probably San Francisco’s most popular rapper. Within the city, fellow Fillmore District native San Quinn remains SF’s icon, but, as Will Bronson, head of SMC Recordings, says: “Once you cross that [Bay} Bridge, it’s Mess.” According to Saeed Crumpler, the rap buyer for Rasputin, the prolific Mess outsells everyone in the Bay save E-40 and The Jacka, often having three or four CDs among the store’s top 20 rap chart. SMC has thus tapped the raspy-voiced gangsta rapper to preside over the just-released compilation Thizz City, first of a Frisco-focused series paralleling the label’s Oakland-oriented imprint Town Thizzness.