Data transmission 0xFFD9 to JPEG, integrated in RAW camera

Question

I want to replace the JPG preview image in my RAW camera files with a JPG camera (I shoot JPG + RAW). I use Panasonic GH1, so the RAW format is RW2. After you finally understood how the RW2 file is organized, I noticed that exiftool can do exactly what I want.

However, I noticed that the JPG preview image embedded in RW2 always has some data that ends with an EOI marker (0xFFD9). Here's the dump (0xFFD9 is at the end of the first line):

0059680: c315 1b0e 5b19 f7a6 f662 d6f2 d4ff d9ff  ....[....b......
0059690: ffff ffff ffff ffff ffff ffff ffff ffff  ................
00596a0: 9290 9192 9392 9093 9795 9293 9494 9494  ................
00596b0: 9494 9493 9192 9392 9293 9395 9694 9596  ................
00596c0: 9292 9394 9697 9491 9194 9394 9493 9394  ................
00596d0: 9493 9494 9393 9494 9493 9291 9294 9394  ................
00596e0: 9596 9492 9695 9193 9696 9595 9694 9493  ................
00596f0: 9394 9494 9595 9493 9394 9494 9494 9495  ................
0059700: 9694 9695 9394 9595 9595 9294 9794 9294  ................
0059710: 9595 9393 9596 9694 9294 9593 9697 9493  ................
0059720: 9493 9394 9696 9696 9596 9593 9494 9393  ................
0059730: 9292 9494 9393 9190 938f 7f6a 4935 333d  ...........jI53=
0059740: 5b75 7877 8892 9393 9190 9192 9495 9595  [uxw............
0059750: 9393 9493 9494 9493 9394 9595 9494 9696  ................
0059760: 9494 9697 9695 9493 9293 9492 9496 9595  ................
0059770: 9495 9393 9391 9194 9594 9494 9494 9394  ................
0059780: 9795 9798 9495 9899 9998 9696 9594 9694  ................
0059790: 9193 9695 9394 9593 9394 9491 908d 7753  ..............wS
00597a0: 3737 567b 8c92 9595 9292 9495 9493 9495  77V{............
00597b0: 9594 9496 9695 9697 9694 9597 9796 9796  ................
00597c0: 9594 9496 9792 9194 9393 9393 9497 9a98  ................
00597d0: 9592 9395 9595 9695 9597 9695 9597 9794  ................
00597e0: 9394 9493 9595 9495 9694 9397 9795 9698  ................
00597f0: 9392 9494 9393 9596 9695 9494 9593 9294  ................

( 400) RW2? , - , GH1? RW2, , , , , 256. , , .