There was a thread here where a couple of people had made scopes with them. I have considered trying one of these lenses myself for NB work.
If I find the thread I'll post a link here. (on my phone at the mo)
Having made several scopes with Surplus Shed lens, 80mm f5, 80mm f11, 102 f6 & 127mm f9.4, I can safely say that the lens' work quite well, not premium quality but very good visually for the price that they are. The construction and baffling of the tube and alignment of the lens cell are just as important in getting the best from the lens as the quality of the glass.
The 127mm X 700mm lens have a good reputation from all the threads that I've read on Cloudy Nights, making a very handy aperture, fast f ratio, portable scope, so I don't think you'd be dissapointed but I'd stay away from the 6" f1.5 as it is an camera lens not an telescope lens unless of course you want to make a large wide angle meteor catcher camera.