probably it's it, there was no other (working) hacks of this game to my knowledge. no idea about 15kHz, is there any problems with that ?
sorry no links. I'm usually do some hacky stuff, share it and then delete (because it's useless for me), but I think here should be links in some thread where...
well, there is 2 revisions of this game currently dumped. there is some chances newer revision "Decathlete (JUET 960709 V1.001)", which was used as base for this hack, had something broken while Sega was trying to fix something else in older original revision.
it was awhile ago and I barely remember the context, IIRC they are opposite to 2 previously known passwords, i.e. disable back some features. not sure if it's totally correct, but if anyone really interested to know he may try to enter one and then another passwords and check result
as was said above - FOV change. i.e. games still works in 640x480 but ratio changed to fit nice on 16:9 LCD screens
it is a bit more complex in case of 3-screen F355 but same principle - they changed view matrix values to make in look good on flat line of 3 screens
you may find cartridge dump in MAME
crack its protection, or decrypt some data or smth else like that
basically same type of task as crack some PC game to play it for free :D
at various points it was Elsemi, Deunan Knute, or me
it's just one of later revisions Naomi 1, you may check some notes there https://github.com/mamedev/mame/blob/140b1ca07adda3edc8b4d0830211f586b97e07cc/src/mame/drivers/naomi.cpp#L86
they was mainly used in games which uses RS232 peripheral devices, like Star Horse or Mushiking series, and number...
it doesn't say that, list at page 4 is about netboot "conversions". the game itself dumped, it's just nobody cared to crack it to boot from DIMM.
this list is way too outdated (~10years I think) and not recommended to use, it also have wrong information in number of places.
only 2 Naomi is not enough, you'll need at least 4 regular Naomi 1/2, plus one more 2x-PCB multi-board main unit, all of them should have comm.boards and should be connected via optical network. each of 4 regular Naomis also should have card reader. only in this case game will work.