Paying for floor replacement ?

my car has sub-frame connectors and I didn't go forward of the trunk so I just used 2 jack stands to support the back half , I used a laser to level it before cutting it all apart and never moved it or the stands until it was back together level , in your case I would use 4 in front and 4 in behind the area you are removing ,all of them on the frame . Make sure it is supported in the air and everything is perfectly level before cutting then do it in sections like do the whole floor pan re and re before cutting out the rockers , check the doors close and line up perfect when doing the rockers but if the car is supported fully by the stands then it shouldn't move if you don't cut it all apart at once .
PS I have a FABO friend whose son did all my welding , he is a carpenter like me and charges his time at $40 an hour for that so I made him take $200 for his time , he was happier than a pig in poop for the extra cash and so was I . I suggest you track down or make a friend like that if you don't weld , the Lincoln welder would have cost me more than that to buy up here in Canada .