I do not understand that sentence. Do you see anything at all on the monitor before Linux starts? If so, what payload? But judging from the payload size, you are using the Linux kernel payload.
No, the monitor is black but is receiving a 800x600 signal, then the mode is set.
I'm using linuxboot payload. I'm using it to load my final kernel and check the kernel and initramfs signatures. I prefer stay with this payload.
Thanks! Jorge