Hi Reagen,
If you are thinking of making these tanks I know you will find interest! Lots of wagon owners have been searching for a solution for years.... Here you can find a thread where a few of us were looking at different ideas.
Second tank in tailgate for WVO conversion
I especially like the two tanks that replace the stock tank... I've had my wagon for 8 years now and have always wanted to do a nice WVO conversion but have never found a good custom tank! If you do end up making these I am definitely interested. Thanks for posting!