So I started thinking about what I could use to make my Pelican box a little sturdier. Initially I went straight for the aluminum plate, I wasn't sure how thick I would need but I guessed pretty thick. Have you priced aluminum plate lately? It's some pretty pricey stuff.
I was shopping for something in Target one fine day and wandered into the housewares department; what do I find but some very nice plastic cutting boards! They had one that was exactly the right size for the bottom of the Pelican and it seemed very sturdy. I tried to flex it with my fingers but either I used to be a lot stronger or this thing'll do the trick. The price was right for $12 so I picked it up.
I went home and using my precision measuring tools (see previous post) I determined that my new cutting board (did I say that it even came in black?) would go right where I wanted it to. I drilled some extra holes in the bottom of my Pelican box, if you've ever seen one you'll be familiar with little indentations around the edges that seem to act as feet, this is where I drilled my holes.
So now you can see I have 8 holes in the bottom of my box. The inner 4 are for the box to mount to the bike and the outer 4 will only be bolted through the cutting board, I figure they'll give the whole setup some rigidity.
Next I set the box on the cutting board and got everything lined up just the way I wanted it. Using one of my existing holes in the box as a guide I drilled through the cutting board. I then stuck a bolt in that hole just to keep everything from moving around and continued on in this manner until I had 8 holes in the cutting board to match those already existing in the box.
At this point I loosely installed some nuts & bolts into the outer holes to hold the pieces together. Looking at the package rack I noticed the area where I intended to mount my contraption was lower than the edges of the rack. Here's where the washers come in from post 1 (please go back and look if you feel the need). A single washer on each hole seems to be enough to somewhat even out the height.
I then set the box/cutting board assembly on the rack and, using the same rubber washer/fender washer deal insert the bolts into the hole. Of course the existing bolts I'd been using were now too short so I had to head out and get some longer ones. But eventually I got it straightened out and the box mounted onto the bike. I then tightened the outer 4 bolts and went for a ride.
Here's the inside of the box when finished:
Here you can see the cutting board on the bottom of the Pelican box.
After a few hundred miles, some of it over very rough terrain, I've determined that this simple mounting plate has stiffened up the Pelican box exponentially and will make permanent mounting very sturdy.
I've found that the Pelican is an excellent size for what I need it to do. I very much like the rectangular shape. I have some footmans loops that I intend to mount to it soon so I can strap some stuff onto the top for camping trips.
Hope this helps someone.