I'm not getting a lot of takers for my request to provide a plausible CT-oriented explanation.
If Buell Wesley Frazier was a witting conspirator (preferably with just self-described Marxist and former sharpshooting Marine Lee Harvey Oswald to keep it nice and simple), he could have planned to say afterwards, if asked, "Gosh, Lee had told me the previous afternoon that he was gonna pick up some curtain rods from the Paine residence, and since the package looked to me to be only 24" to 28.5" in length when I kinda glanced at it over my shoulder and out of the corner of my eye real quick-like on the back seat of my car this morning, I figured that's what it was, especially after I asked him, 'What's in that twenty-four-inch to twenty-eight-and-a-half-inch-long package you put on the back seat before we got into my 1954 Chevy sedan, Lee?' and he said, 'Don't you remember, You Big Dummy, I told you yesterday TWENTY-FOUR TO TWENTY-EIGHT-AND-A-HALF-INCH-LONG CURTAIN RODS!!!!'"