Path looks like you came a long way.We usually don't split the roof in the middle length wise.It causes a lot of extra welding and warping. We lean the posts in and adjust the window channels to fit .I have never seen anyone string a box around the work area like that and welding braces inside usually helps hold the body during construction.But hay if it works for ya great!Now would be a good time to make it a 2 door hint hint.If ya do, lengthen the front doors.You will be glad you did later. The rear window lowered looks much better. Word of advise,rool the car outside and stand way back to see if everything looks in proportion.Up close it may look good but I have found it helps to look from a distance. My wife has family in Argentina,real nice people.That is cool you are building a Kustom. GOOD LUCK !