Next experiment: Yoshi's Island with no cart in the top - black screen. Yoshi's Island with original Yoshi's Island in the top - gets to the Nintendo screen and does that black flicker thing when you reset the console and hangs.
I thought sram was for savings games rather than using as "ram"? All other games are using the Super UFO's built in sram, presume if the plug through actually worked it would just be using the chip. Surely if it used the donor carts sram then you'd wipe the original cart's save?
Are there any other programs that can change headers?
OK, ignore all that. I've got the plug through for DSP plug through working with Mario Kart (U and E), Super Air Diver 2 (J), Final Stretch (U) and Pilotwings (U but not E). No need to load into DRAM or run in hyper mode.
I've just bought PGA Tour 96 off ebay because it was the cheapest SA-1 cart I could find over here, so I'll test that with some of the Kirby games and SMRPG. I've already seen a video of someone on youtube being able to play Megaman X3 with an X2 cart in the top, so it looks like CX4 support is there as well.
ucon64.exe --pad -ufos YOURFILE.SRM