Dunno how ya got it so lite!mine came in at right at 8 pounds. I tried a 15/4 and it was pretty anemic. Goes much better with a 16/4 W.
not sure of the meaning of magnum #1 fuel either but I just run 15% morgan fuel.

of all my planes this one has the worst thrust to wieght ratio. I've always way over powered em. when I bought the 100 I thoght it would kick A on my 91's, it barely out does em. Not really sure its as strong as one of my 91's it is very close tho. I had the 180 on a dp ultimate that was 9 1/2 pounds and it was perfect . figure Ill lose 1/2 a pound puttin on the harrier. I might have to do it. just need taller gear.