help!! trying to cut the top

I have a 2000 Mercury Grand Marquis and I know that this may sound a little crazy but I am trying to cut the top off to put a removable roof City on the frame but in order to do this I know I must stiffen up the frame I have seen some cars have a support bar in the middle of it I think they call it a sports bar will that be sufficient enough to keep car from bending when making a hard stop and will it be enough to stiffen up the fram to support the roof being removed

Sounds interesting, do you have any pictures of the city? It all depends on how heavy it is. How heavy is the city, are we talking over 200 pounds?