Roof leaking - Repair recommendations and floor template

[Toro]

Hi everyone, long time reader and seldom poster:

I bought a 2000 E-250 5.4 gasoline Salem Kroger conversion about a year ago, very low mileage, mostly well preserved, however, it had 2 manual sunroofs installed that were beyond repair (one in front over the cockpit and another to the back, square). I ran into some hickups with this as I live in Panama, Central America, and the rainy season lasts on average 8 months, that's 8 months of almost daily torrential tropical downpour. I managed to get another sunroof for the front and a maxxair fan for the rear, however, both were smaller than the original openings, so I got some metal sheeting cut to size and riveted them on then applied for the front polyurethane and for the back butyl, and for the most part initially I was fine but now water is trickling in at an alarming rate. I was told to be careful about welding the roof because of several risks, so I would like to know opinions on this and what my best course of action could be.

Also, would anyone know how where I could get a floor template for this model or suggest an efficient way of making one for the flooring?

I appreciate any and all recommendations. I will try and get some pics of the roof for reference.