[coreboot] Need a bigger CBFS size. What's a save value?

[David Griffith]

I'm experimenting with a Thinkpad T60p, specifically getting something 
working that includes PXE and secondary payloads.  Apparently the default 
CBFS size of 0x40000 is too small because the build process complains it 
can't add ipxe.rom and guesses that there's no room.  Just now I tried 
specifying a size of 0x200000, thinking that would work because I have a 
two megabyte SPI flash chip.  I went through the procedures on 
https://www.coreboot.org/Board:lenovo/t60 and 
https://www.coreboot.org/Board:lenovo/x60/Installation which led to a T60p 
that shows a black screen and is non-responsive.  So, I guess that was a 
wrong value.

So, what's a safe value for the CBFS size that will allow me to add PXE 
and some other secondary payloads?