MassiveD really has got a point, that has me really thinking. You posted to ask about your idea for frame geometry, i went with that angle. We do not know anything about you, background/ experience, tools owned. I am not trying to discourage you, but there is a lot of stuff to frame building, it's definitely as easy as opening a can of beans. I had been a welder for 8 years, ended renting a torch, ordering tubes and successfully built a tandem frame. One cool thing I did discover with lugs is unlike aluminum, you can see how much you can stress the lugs, to get a a slanted top tube. Its not as commiting. the butting is opposite between aluminum and steel seat tubes.