We live in a doublewide mobile home and when we first moved in we had a back deck added to the length of the home with a metal roof over it. The metal roof has always leaked here and there where it connected with the mobile home roof. Upon checking it out, I found that there was not enough flashing. The narrow flashing had been tucked under the shingles only a inch or so and water appeared to be backing up. My son and I climbed on the roof with wider flashing and removed the old and put on new, tucking it several inches under the shingles and sealing it with roof adhesive. After doing so, I realized we screwed the flashing to the metal only on the metal roof. While there are 2x4s under the metal, we didn't hit them when we screwed in the flashing. My husband is BESIDE HIMSELF. He says when it snows the weight of the snow will cause the screws to pop up and we'll have LOTS of leaks. I offered to go back up and put in screws about 4 inches up from our current screws where there are actual 2x4s and leave in the other screws. He says this will only cause them to pull loose now. Is there such a thing as nuts to go on the underside of the metal screws? Is any of this a worry and if so how should I fix our screwup? Thanks for any and all comments.