Gene,
The Venom is much stronger than the Viper fuselage. It has 3/16" sides and a lot more reinforcement.
I was going to effectively give away the cores. But my wife keeps telling me to stop giving stuff away. I can't go any lower than $65 for the fuselage and tail kit *. I updated the [link=http://www.stegallhobbies.com/Q500/Venom/Venom.aspx]Venom[/link] page and changed the price with a foam core to $75.
I can fit quite a few kits in the smaller shipping box and save a couple of dollars on shipping. So get a group order together.
* I don't really think the full size plans are needed, and I can knock off $5 per kit if the plans are omitted.