when u tack with the welder jump around do a few on the top, then the bottom, then side to side. if u stay too long in the same area youll warp the sheet. so take ur time id recommend practicing ur weling on a test panel first and get ur welder dialed in before you jump onto the deck lid, and when ur finishing use a block as said. if u dont kno what im talkin about this is what it looks like basic 6 inch sanding block
