Cool, I used to have the string and plumb bob CG thing set up in my old shop, as long as you knew the datum line you could get the CGs dead on as I recall, been A while.
One little thing, the better the scale the better the results. I use my fish scale for weighing planes but I have to keep in mind this is A fishermans scale and it's MY fishermans scale, it tends to make things just A bit heavy if you know what I mean. I would build A plane for someone and they would pick it up, I have all the stats ready for them too. Then they get it home and put it on A real scale and they are even more thrilled, it came out way lighter then what I told them.
Anyway, it works well on trout!!