'Frazier consistently describes the package being about this long'
Frazier consistently repeats that he wasn't paying attention to the bag.
That fact does not require speculation.
I agree, Frazier emphasises that he doesn't pay that much attention to the bag and there's no reason why he should, Oswald has already explained what it is and Frazier has no reason to doubt him.
However, he
does see the bag and provides the following description from what he can remember:
"It must have been about 2' long, and the top of the sack was sort of folded up, and the rest of the sack had been kind of folded under."I did an analysis of the construction of CE 142 and concluded that it was specifically designed and constructed to carry something 27" or less. What I found interesting was that Frazier's description of what he saw is a perfect description of what CE 142 would look like when being used.
The point is - CE 142, being used the way Frazier describes, could not carry a rifle even if it was disassembled (I don't buy that the assassin would bring a disassembled rifle for one second).
This doesn't mean Oswald didn't bring a rifle with him that morning. Elsewhere I've argued that Frazier deliberately underestimated the length of the bag because people wouldn't believe he didn't recognise it as a rifle in a bag. If that's the case CE 142 was not the bag Oswald used that day.