Sure you can use as much BW to recon as you see fit, as long as it is a decent enough amount to put it in solution.
Volume alone as standard measurement of a solution is not the best way in my opinion to figure out concentrations. It is dependant on the fact that everyone is reconstituting the same weight (mcg/mg/iu) in the same amount of solution (1ml, 2ml, 5ml, etc). So volume comparisons between differnt applications can lead to incorrect conclusions, IMO.
One man's 1cc is another man's .5cc, if one used half the BW to recon? Or one man's 10 tics is another mans 5 tics on a slin pin.
On a differnet note, a 1cc pin has 5(2 tic) increments per cc and a 1/2cc pin has 10(1 tic) increments. I know a few who took both to meant he same, thus one was OD-ing doing 40 tics instead of 20, because of the pin used...
Important thing is just use the amount to recon that suits you and figure out the volume needed to aquire the desired doseage, and go from there. Doing the math yourself correctly goes a long way to being mistake free.