In reply to Greasy Prusiks:
There was a news article or forum post on UKC several years ago about the post-accident activities of a lass who'd broken her back in some injury related to a pull up bar (if I recall correctly.) I can't find it by google however. I don't know what the legal aspect to it was (if any). But it does underscore the potentially serious consequences with this stuff.
As well as insurance, do consider the means by which you sell the boards. If you sell them personally, then liability falls to you and - in my mind - there would always be uncertainty about what I would be exposing myself to now and forever more. I personally would find this unpredictability to be very bad as given the cost of spine injuries if something ever happened and there was a law suit it could be the ruin of me. Very small risk, very high consequences.
If you form a limited company, then so long as your actions remain legal then any liability incurred by the trading of the company stops with the company. Your personal finances and house remain safe. Running a small company is not a significant amount of work, but there are significant penalties for late filing of specific paperwork items etc. I suspect that in order for liability of equipment failure to stop with the company, the company would have to have a documented testing and quality control approach to the products. Would you be happy selling something that could cause injury without doing this, company or not?
I appreciate that this is a very negative take on things, hopefully someone will be along to balance it out!