Rob - One tip that might really save a lot of time. I hot glued 4 pieces together at once that would span the opening of the area that you want to cover. But don't glue them flat (Cause your deck is probably rounding like my double was) glue them together while lying over the area to be filled to match the curvature of your deck. Then trace from underneath, cut, and wa-la. You have your triangle completed, 4 strips wide. It is a little tricky to get a perfect fit for a 3-4" length on each side, but with patience you'll get it satisfactory. You can do the same for the rear (But I'd try 2 or 3 at the most).

Another tip that might come in handy. Most BB posts show spanning the recess from side to side every few strips to lend support. I started from the front and back like "THE BOOK" says, but after the first few strips are installed (front and rear), I clamped a strip under the previously placed strips from the front to back, and used this for a ledge for the others to "rest" on while they dry and level. This ledge comes in handy as you can clamp every second or third mini srtips in place while they dry and work from side to side. You can put a dab of hot glue on the top towards the inside to speed up the process. One thing that you will have to do is to pull this "support ledge" strip down to match the curve of the recess. To do this I used a piece of duct tape and pulled it "the ledge strip" down to a screw in one of the forms underneath to match the curve.

It worked well for me, maybe it will for you!

DAVE