I heard from my buddy. He thinks he'll have to make some modifications to boot box. He says he may have to cut out a little in the front and a bit of the bottom, too. He said he may raise the whole bottom a little bit because he has the muffler under the box.
He got them from Dunnell Engines in the UK. Their phone number is 011-44-1449-677726 (that's probably for calling from the US). Ask for Paul Dunnell. As I assumed, he can make another copy quickly and economically since he already has all the measurements and drawings. If Dean can get away without modifying his boot tray with his design, I suspect you could too and there may be some small changes to this design that would allow using an unmodified boot tray.