I did it to a junk 76 I had in high school. Even if it's slammed the kids will probably have trouble climbing over the sides. The doors didn't open reliably after a few days of hooning.
Apparently the roof adds a LOT of structure to the body! Maybe a full cage would mitigate the flex and keep the doors working right, who knows. I imagine the top of the "floating" b-pillar would beed to be tied into the cage to keep it from flexing from the weight of the rear door. Mine eventually bent so that neither the front nor back door would close.
It wasn't really fun riding with no top or doors (finally cut the b-pillar off at the floor and hucked what was left of the front doors off. Expect LOTS of attention from the authorities...