Pye Wackett - amazing how one keeps hearing about cancelled projects from decades ago. One wonders what else may yet be revealed!
I'd never heard of Tag Board until I saw a D-21 on display at Palmdale in 1999, though I presume it had been in the public domain for some years by then. Fascinating reading about it.
I must get myself to Dayton - B-36, B-58 and XB-70 are three types I've never seen in the metal...