I have no experience with this kit, but pictures may help with more responses. I am currently building a HOB P51. The 1/32" ply doublers fit well on my kit, you glue the doublers in place according to the plans, and trim the balsa to match the ply. I made the mistake of making two left sides. Pay attention upon making the second side. Hope this helps, as I have not seen the FW190 kit I am only assumming it is the same as their P51.

Good Luck