I met Kent Silk, owner of Texas Sidecar Company, last week at the Janus Motorcycle owners rally. I didn't ask about the Bonneville America specifically, but was impressed with his expertise and experience.
The TSC company website,
TSC, shows pictures of sidecars on BAs.
Give him a call. He's easy to talk to and will take the time to answer all questions. Kent Silk at (254)218-3990.