Yes I did the redesign to insure light weight. Two things burn E-fuel, weight and speed.
The Arrow was not a large airplane that could be easily lightened and is what I competed with in the 80's.
I built only one from the MK kit the other 5 ware scratch built foam wing copies running 7 - 7 1/2 lb.
I piped the SO 61VF conservatively between 13500 - 14000 on the ground until I needed to reduce the sound level at one of the fields I was using. I added a soft mount and lengthened the OPS pipe about 2 inches and mounted a slightly modified 12-9 prop, dropping about 10 DB. The first thing I noticed was how it pulled away from the corners in a square loop with half rolls. We use to call it 'Grunt'. I also found that I used about half as much fuel and a glow plug lasted most of a season. With this behind me I was ready for turnaround with a different airplane, beginning the still evolving 'Option' series.
Jon, I'll send you the drawings.
Jim