Great, thanks for testing.
I think what helped was the sync'ing to reset, so instead of enabling the cart lower rom, clearing ram and jumping to 0x0. A hardware reset is performed and starting the cart, as "lowerrom" from the cart is forcefullly mapped at 0-3FFF. Also for plotting iirc. it was expecting to see physical cart rom 1 at logical rom 1 (so it would be mapped to all logical roms, kinda like basic rom is on cpc, when no other roms are overwriting it).
Good news, hopefully others have similar results. Other fun thing, is I managed to start Barbarian 2 cart on my regular cpc6128, I suppose it uses no plus feats at all
Sorry to say that things for me are worse with Beta 5 of this firmware.
Robocop II - Crashes at the title screen - no longer able to get to the game
Navy Seals - starts and displays
Pang - screen goes black and nothing further happens
Switchblade - works
Crazy Cars II - Gfx corrupt on title screens and when games starts it crashes
Fire & Forget II - Gfx corrupt on title screen and then goes blank
Tennis Cup II - seems ok but I can't play it
Panza Kick Boxing - some gfx seem corrupt/out of place
Copter 271 - starts to display Loricels logo but crashes
Klax - works
Dick Tracy - Title screen and music displayed by when select Music/Fx Sound it crashes
World of Sports - Shows a black screen
Operation Thunderbolt - Shows a black screen
No Exit - Title screen and menu work but then shows a black screen and stops
Pro Tennis Tour - no longer works
Tin Tin On The Moon - Intro sequence works but with corrupt gfx and now games seems to work
Batman The Movie - title screen shows but then goes to a black screen and stops
Mystical - Starts but then crashes when starting game
Burnin Rubber - Starts but then goes to a black screen and stops
Plotting - Starts and displays title screens but when try to start game crashes
Pinball Magic - Starts but you can't play as ball drops out everytime
If I quickly switch off and back on again with power switch some games like World of Sports start but crash soon after.