Playing with the sourcecode, I usurped the 8:7 PAR to be just 8:7 like 4:3. The switch that controls this is a boolean and I haven't the time to change it right now (and then I would need to make a github account to request a pull for the changes).
@matchaman if you use lr-nestopia you only use one button. L1. And you can map it to select. Select will still work the same. If you are in actual gameplay and you hit select it does not eject+ flip while you are in game. But if you say hit select once in gameplay when you get to the flip disk screen it will give you a disk side error. All you have to do is press the select button one time and it will correct itself. If in game you hit the select button an even number of times like 2x, 4x, etc... it wont give you the error. Not a big deal when you do get the error as you only flip a disk once or so while playing so you lose maybe a second of time. Again you need to switch to lr-nestopia as this does not work in lr-fceumm
I did some further testing for some new translations that I patched and I have to do a bit of embarrassing back-pedaling here. I'm not too proud to admit when I made a mistake. :)
L1 in lr-nestopia does "everything" in the RetroPie. It will flip the disk and load it, and it won't do this when you're not being prompted to flip it, so there is no danger that it will screw up your game. I will resume testing on FDS for now, but there has been 1 rom out of about 6 or 7 that I've tested so far that boots back to the romlist in lr-nestopia, so that leaves us with lr-fceumm's completely different system for loading. I'm assuming there is nothing that can be done to fix lr-fceumm to behave like lr-nestopia since the XBox version of NestopiaX has a similer "flip disk" command in the menu that behaves identically to pressing L1 on the pad in RetroPie. (Actually, this is one instance where I prefer how RetroPie handles things).
There still is the issue of hotkey mapping though. There doesn't seem to be any good way of doing this on a per-system basis that works. Is the information on the github in the following link bad now?
@flyingtomahawk I’ll admit I did some searching to look into where save points were in the game since I am not very good at Castlevania and I didn’t know where FDS would ask you to save. I’m glad the issue is resolved.
The reigning theory is that the issue comes from missing HEADERS. The NES requires Headers in the ROM or it won't boot. However, just recently posted information suggests that unzipping the ROM may solve the problem. I've not been able to test this myself since I'm troubleshooting controller issues right now. Please let everybody here know if unzipping works for you!