Puzzle Bobble on CHA 42G-3

[ArcadeTV]

I want to make a Puzzle Bobble for the kids, so I got a Super Sidekicks 2 MVS cart which was supposed to have a PROG TOP and CHA 256, but it had a PROG 4096B and CHA 42G-3.
The PROG board works fine after concatenating the four V roms into 2x 27C160 and removing the jumpers.
I used the roms of pbobblen from the latest mame 0.235.
The sprites are all wonky, except for the s-fix, so I suspect the arrangement of the C roms to be wrong. Tinkering with the jumpers didn't help and before I mess with 6 roms in place, I wanted to ask you guys for advice.
Reading here that the data has to be composed differently on 42G boards IF 2 MiB roms are used, but I have 27C800's on the cart, so I thought that does not apply.

In the mame driver's source code it sais that C1 - C4 are unused, I wonder if C5 and C6 can then be used as C1 and C2 or if C1-C4 need to be present.

Here's a picture.

Thanks for any help with this, it's very much appreciated!

 

[ArcadeTV]

I've put C5 in place of C3
and C6 in place of C4
as seen on mvs-scans.com the Bust-a-Move pirate images.
Works!

But why is that?

 

[grobda]

ironically i got a bootleg puzzle bobble on an original cart with a cha 42g-3. if id seen this sooner id have sent you the roms as i wanted to convert mine to last resort...

after a lot of swapping and headscratching with what gfx went where, i finally got it running by burning 2 copies of concatenated c1/3 and c2/4 in c1/5 and c2/6 (all 27c160). i dont really understand how/why it worked, although i suspect the /ce lines are looking for the same data from different sockets, i couldve probably tied some /ce lines together for the same result.

edit: seems mame drivers just map graphics roms sequentially and dont really emulate how the carts address that memory. /oe lines on a cha 42g-3 are all wired to ground and bank selection is done with /ce via a 74LS139; C1/2 goto pin 4, C3/4 to 5, C5/6 to 6 and C7/8 to 7. So i just lifted /ce of c1/2, wired to ground and the game worked, saving the 2 duplicate roms.

the prog board (prog-g2) just needed v1 and v2 concatenated onto a 27c160 and a small hack to the back of the board removing.