Am just putting a new table together, with a box section frame & a waterjet cut 1400x800x15mm mild steel top. All good except the plate turned up a bit more warped than I'd like. Is probably only +/- 2mm, but enough to be an annoyance when clamping larger pieces. Considering my options for getting the top flatter, and wondering what has the best chance of success? I have no experience of trying to move anything this thick. Add some additional 50mm box section cross members, bolt down the high points & pack up the low points. (What will move first, the table top or the frame?). Try to press it flat with some C channel and a bottle jack. Invest in some oxy propane kit, and have a go at heat straightening. (Have no experience, but always keen to learn new skills). Open to any suggestions suitable for a home workshop, thanks!