OK, first question... go back and read the first couple of pages of the thread I didn't weigh the pipe and header, Dick Hanson has posted the weight somewhere in one of his post, I've forgotten for sure but think it's in the 9-11oz. range.
I asked about the header bolt hole spacing in the MVVS suppost forum and Dar Zeelon quickly replied and included a diagram. the bolt hole spacing is 36.5mm. The diagram is in the "MVVS 1.6 exhaust" thread in the MVVS support forum. The Zenoah G-26 bolt hole spacing is around 35mm (ask Ralph, he can tell you for sure what it is) The Mac 25 bolt hole spacing was a couple of mm less than this (sorry, I didn't measure it, I just put it on the mill and slotted the holes to make it fit)
Mr. Hanson has stated in his post about the pipe/ header combo saying that it is a broad range pipe that is already tuned for the rpm range we'll most likely be running in (Plug and Play, just put it together with a gap large enough to keep the pipe and header from touching) Overall lenght of the pipe is around 27.5in. from the center of the header to the end of the pipe.
AAAAhhhh... that Ryobi. I'll have to get my homemade header welded sometime and the next time I try it I think I'll have to use a smaller prop. That 18x8 on the pipe was causing so much cylinder pressure that I was about to blow the base gasket. I'll get back to it somewhere down the road. For now, I've got a new Homelite 30 that is begging me to soup it up.