You should have told members which boat that it is but I'll cover that. He has the DPI 1/4-scale OB tunnel.
OK, I don't know if they put any wood in the transon under the plastic or not. The only way that I know of totest that would be to drill a small hole where one of the mounting bolts go. If you strike wood then I'd go with the threaded brass inserts. If not then you've got a problem.