Mark,
This was actually a postal approved scale, and it is always accurate against the post office scale...besides, if the real weight is off a bit, it still would be very close to once ounce gained. (ie if it were really 14.4 to 15.5 instead of 13.3...)

As for the epoxy not being as strong, when you try to pull the sheeting off of a scrap piece, the foam always stays attached to the balsa...so the foam is the weakest link..

ZZ, It is more expensive until you take two things into account...

1) If you do not use the epoxy this year it is toast anyway...

2) When doing a small part, one "pump" is too much so you will have to throw away glue anyway.

Rob