A boomerang is the same thing as a cobra roll just like the flatspin is mostly the same as a corkscrew, but it depends on which company you have. B&M has cobra rolls(are wider than boomerangs and hang further down), flat spins(a mild variation on the corkscrew), and zero-g rolls which are different from barrel rolls but are of the same concept. The first inversion out of the tunnel is a zero-g roll because you do feel weightless and that's what B&M claim it as(enough said). The other inversion is a corkscrew, there is no rule that says it must level out after it inverts!
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Steel- 1.Millennuim Force
Wood- 1.The Beast
"We're not worthy, We're not worthy!"