he can do what he wants with the design its a tried and tested desng and it holds up very well if he can make it to a good standard why shoudlunt he be able to they are not patented that i am aware of and im sure there would be differences in the two products material for one, im sure the offset would be somewhat differentthe type of welding done on them i presume would also be different. sell them if you can they look like a great product