To clarify my outlook on this firewall.....

If I had been building this thing from a kit and seen a two layer liteply firewall, I probably would have used it as a pattern. You've got to remember that the center top of the firewall has virtually nothing behind it either supporting it or connecting it to the front of the fuselage. Yes, there is the top of the fuselage that butts up to the top of the firewall, but that fuselage top is foam, sheeted with balsa wood (looks about 1/16" balsa). The sides of the firewall have adequate connection to the side formers of the fuselage, but the center top has really almost nothing. So I would have wanted the firewall to have adequate strength from side to side.

One of the first modifications I'd have made to a KIT of these ARF parts, would have been to place some kind of bulkhead across the inside top that would have given the firewall some support. It could be another piece of liteply. That's what I've put into mine during the repairs. As it comes in the ARF, the firewall is supported in basically a "U". Down the sides and across the bottom is nicely connected to fuselage sides, bottom and bulkheads. And a liteply firewall just isn't going to do much of a job being supported on 3 sides only.

I would suggest to the mfg, that he not sandwich two layers of liteply, but at least replace one with good 5-ply. And add some support for the entire front top of the fuselage to bridge that gap. Go back and look at the middle picture. All that open area is still open area behind the new firewall, just like it was behind the liteply firewall that had it's center punched out. A crossbrace or two??? Like between those two tabs that stick out into the opening. I was amazed that those two "tabs" were there. I can't imagine any reason whatsoever to have cut out the intervening wood. It would have helped stiffen that firewall, and was simply waste when cut out. (Or maybe some other part was taken out of that area, who knows.)