Oh dear Dave You have problem with Your nerves.
Get some rest.
It is of course no secret that natami/vampire/apollo in higher resolutions suffers from a lack of bandwidth.
And in higher resolution performance of natami/vampire/apollo really drop.
Below 68060 80 MHz.
There is no reason to use natami/vampire/apollo in 640x480 8bit.
All test should be made at least at 800x600 16 bit.