force-power curves

I’ve acquired a fitrodyne unit that measures the speed of the bar and built force velocity and force power curves.
I have a problem with the squat though. See, when I calculate power with the load on the bar (P=Force x Velocity) then I get a nice bell shaped curve with an apex which indicates clearly what load allows maximum power production ( around 60% to 30%) depending on the athlete). But if you add the athlete’s bodyweight to the weight of the bar (which is quite logical since during the test everybody ends up going airborne with loads up to even 80% of max and finishing up on toes on heavier loads), then the power curve does not come down anymore! the greatest power value is with an empty bar! and since I can’t really unload the athlete I’m not even sure VJ yields the greatest power…
Christian,an opinion as what it could mean in terms of planning?

thanks