RE: bought this at a club auction...what engine?
IMO, if it weighs about 5.2 lbs. now, without covering...then figure about 5.75 to 6 lbs. after. (that's figuring with an iron on film covering...not paint )
Is there any radio equipment installed? (doesn't appear to be )
Figure about 6.5 to 7 lbs. after covering and radio, pushrods, etc.
With an 80" span...hmmm...a 2 stroke .90 would be about what I would use, at minimum...probably more like a 1.20
A 2 stroke .90 / .91 will add at least a pound and a half...so...you're looking at getting close to 9 lbs. all up wt. (maybe a little bit more, with fuel )