The only plan I have seen is at the link below. It seems to be about the same size as your current pipes. It uses the 207 instead of the 206. I have been considering building another set of Voigt pipes for my Audio Nirvana 8" drivers, whose T/S parameters are close to the 206. I will make them in a slightly larger cross section, dictated by the 11-1/4" width of the mdf boards I get from my lumber source. But hardwood would look really nice.