This book was written by Don Hewes. He describes modifications he developed for his BD-4. There are numerous hand drawn sketches and an easy-to-read text. The modifications are very much thought through and are invaluable improvements to the original design.
Don Hewes died a few years ago and the book is no longer in print. You can however, download an Adobe PDF document from a scanned in image of it:
hewes.pdf (6 MB, right-click
here and select "Save Target As..." or alike.)
hewes.exe (6 MB, or if you have problems with the upper link use this
self-expanding ZIP archive)
You'll need Adobe's PDF Reader 
Don's plane is now owned and flown by Stan
Dauncey in Great Britain. Check out his profile
for pictures of the "Verginian Patriot".
Note: When you do the modification to the landing
gear box be aware that there have been problems reported, due to the decreased
stability of the lid. Search the newsletters for information and fixes.