My fastest time was the Phenoix Giles. I assembled it exactly per the book. I even used the supplied hardware.[X(]
From the box too the runway was 6 hours.
Giant Scale ARFs usually take me a couple weeks.
I think you should just add a Zero to the time listed on the box.
If they say 6-8 hours, then I usually figure 60 or 80 hours to get it going. If they say 16--20 hours, well, then I figure about 160--200 hours.