setting bootverbose (or boothowto) from the kernel config file ?

In a diskless setting which does not use /boot/loader, i need to
control the value of 'bootverbose' to print extra debugging messages.

I just learned that using this line in the kernel config file

	env	"my_kenv_settings"

and providing a list of var.name=value in the file my_kenv_settings,
these values get dumped to compile/MYKERNEL/env.c and become accessible
from the kernel through getenv() (e.g. i used this for machdep.bios.pnp).

However i haven't found a way to set 'bootverbose', which is a sysctl
variable (debug.bootverbose) so it seems to be in a different namespace.

Any ideas ?

Also, what is exactly the relation between the two variables
'boothowto' (apparently set through the loader and containing
various flags) and 'bootverbose' (which is a sysctl) ?
Different parts of the kernel use one or the other to control
verbose output, and i am not sure if, e.g. setting RB_VERBOSE
in 'boothowto' also sets bootverbose...

	thanks
	luigi