Given optimun enclosure parameters
Vb=1 cu.ft
Fb=30Hz
F3=35Hz
Lv=10 inches

Will decreasing the port Lv have the same effect on Fb and F3 as if you had decreased only the volume Vb.

In other words, if I decrease the optimum volume to ??? cu.ft and obtain a new Fb=40Hz and F3=50Hz, is it possible to get these same new parameters by just shortening the length of the vent and keep the optimum volume?