Re: Can't decide on top tube
You must be feeling pretty proud of that bike by now. I would have voted for the up position simply to give more room for the engine. Never know when you want to put a more powerful engine in there. I think a 147cc Jacobsen 2 stroke would fit your frame if you ever get the itch for more.
But what you've done with the broke back is real good and sets the bike apart as different. The gussets are winners and help to set it apart visually. And the drilled out holes in the gussets give a nice 'echo' to the circles motiff of wheels,hubs, etc. Another nice roundy shape would be a cylindrical tank behind the seat. Yes, lay the seat back a bit and give it a tank behind the seat. That would be my vote.
As a newby welder myself I gotta say you're doing great with the welding. You're quicker than I am. I couldn't tell what welder you got but it must be a good one. A welder and a side grinder sure open up new possibilities. Well done, sir!
Someday when I grow up I will probably lose interest in toys with wheels, but until then...