There are a handful of statements that support my thoughts about the bank bag and the dummy reserve.
First, witnesses that saw the money bag being brought onboard the jet describe it as about "1' by 2'" in size.
Second, we do have the dimensions of the money and from there can measure its cubic space (the volume it occupied).
Third, Cooper himself complained he would have to use a parachute to pack the money (NOTE: The next size up bank bag is about 3' tall, meaning if that bag was used there would have been a significant amount of excess bag at the top to cinch and there would have been absolutely no reason for Cooper to complain he would need to use a parachute to store the money).
Fourth, Tina witnessed him wrapping or attempting to put the money in one of the reserves. Now she may have assumed it was the pink parachute and been wrong about that. Or, perhaps Cooper tried using the pink parachute and abandoned the idea only to use the white dummy reserve after she was in the cockpit.
Fifth, the pics I displayed showing the bank bag sitting next to the reserve doesn't adequately capture the size difference. If I had to guess I would say the volume of the bank bag is double the volume of the reserve. This is plainly obvious when holding the two and looking at them side-by-side in person.
Sixth, the FBI documents do mention a "white material." Perhaps it's an error, perhaps it isn't.
Seventh, the dummy reserve is gone. Why?
Finally, I suspect--taking an educated guess--that DBC opened up the dummy reserve and wrapped the excess twenties, attache' case, and perhaps some other smaller items (yellow bag he boarded with, notes, etc) into the white canopy and used some of the shroud lines he cut from the genuine reserve to secure that "bundle" to his person in some manner. Remember, Cooper cut off 79.6 feet of shroud line from the genuine reserve. That is a lot of cord. Are we to believe it was all used on the money bag alone?
Also, consider that smokejumpers are accustomed to jumping into the forest with chainsaws, shovels, backpacks and all kinds of shit dangling below them. While not easy, it is certainly doable.