boot block differences between 4.x and 6.x ?

maybe some of you know the answer here...

the revised picobsd script (attached here, it uses
sysutils/makefs instead of vnconfig/mdconfig so it can
run as a non privileged user) that i was using to
create images with the 4.11 boot blocks (boot1 and boot2),
does not seem to work anymore with the boot blocks
taken from 6.0 (and so, -current as well).

When i force it to use the 4.x boot blocks, all is fine,
and the picobsd.bin produced (built on 6.0 using 7-current
sources) boots fine on qemu.

I am a bit puzzled on what could be the relevant change in boot1/boot2
could have caused the loss of functionality.

If that matters, picobsd bypasses /boot/loader and goes straight
to boot /kernel (the name is patched into the boot block,
but it does not matter because the new blocks do not
even get to the point of showing the 'missing /boot/loader'
error message).

does anyone know where should i look at ?

	thanks
	luigi