setting dumpdev while boot on 7-CURRENT

Hi

I am trying to figure out how to setup dumpdev while kernel build or
from loader.

Looks like it is impossible to use old (very old) way with flags.

dumpdev loader variable described here:
http://freebsd-man.page2go2.com/man8/loader_8.html

is not work and event not present any more in laoder.8:
----------------------------
revision 1.70
date: 2004/09/30 15:27:37;  author: ru;  state: Exp;  lines: +0 -7
Setting dump device from loader(8) has not been supported since 2002.
----------------------------

Any hints how it should work ?

-- 
Vladimir B. Grebenschikov
SWsoft Inc. vova_at_swsoft.com