issue with AMD Demon floor pan..please help newbie

Man I've done alot of AMD pans and they all need tweaking but i have never had one fit as bad as yours, The last one i did was done in 1 day with a little amount of fitting,
And yes always start your plug welding on the cross members first. And finish at the pinch weld and seat pan.If ya can't get it to fit tight on the x members i'd send it back and get a replacement.