Great question! I have been told all my life that you can not cut the tops off of cars without re-enforcing the body because they will bend. I call BS on that! I have cut the tops off of many cars and never had a single one bend! I cut the top off of a Toyota Tercell and used it as a desert toy for a season and it never bent. I installed nitrous oxide (sneaky Pete system) on it and we jumped it all the time. I cut the top of of a VW Bug about 12 years ago and it is still going strong, unbent. I cut the top off an Isuzu Rodeo and my buddy drives it every day and off roads it all the time, still straight. I have also cut the top off of an old mail Jeep, a Chrysler 5th avenue and a few more.
Do it! The only problem is the windows will be hard to crank up and down without the window tracks and you will get wet if it rains.
Don't be scared to do it!
Your car sits on a frame. The frame will not let it bend in a V
