Mike those wide decks are great, but that steel they used was simply wrong. One thing that I would consider if I was you when you put it all back together is to omit the rubber mat over the top of the new deck and have Rhino-Liner or Line-X 2-part epoxy material sprayed onto the deck instead. It will bond to the surface, no water can get under it, it is durable, and it looks good. JMO.
BigAl used it very successfully on his KT7. You might want to consider it. If you have a modest air compressor, you can do spray the liner material on yourself.