BADDANDY
Adventurer
At 50" apart, which I'm assuming you mean measuring left to right of the vehicle, you might run into some issues. The hardtop on the inside is double walled for added strength, joining the sides of the hardtop with top portion of the hardtop. Mounting surface also angled. I had to choose a spot on the inside of the last roof strengthening ridge on either side to get a clean mounting surface. .
Yes, I've read a few threads and by everyone's opinion, the double wall is the strongest place to mount them. I also will run an aluminum strip on each side to use instead of washers. If the thickness is good, I'll use T-nuts and paint the strips and nuts white so nothing will be barely seen on the inside.