Was testing off line, alt 5k base
bomb load 40/500's,  fuel 50%,  You will need to lift nose at end of runway.
fly on stall limiter, tried with 2 notch's flap, had hard time, with three notch's of flaps a little easier, once up reduce to 2 notch's then one to none. 
always use takeoff power (wep), I agree standing on the brakes when starting
well help a lot,  Make sure no hill in  front of the runway for a very good distance, like ten to fifteen miles, you will need all that space to get into a good climb rate.
This BFB climbs very well with that bomb load just under 1000 ft a minute, speed was about 220 mph ground, still testing off line.
well update any other findings   DHawk