I have a TF Spit waiting a turn at the building table. It was not designed to be glassed for strength, and is structurally sound without it, so glassing would be for smoothness. IME, glass is messy, expensive, hard to work and can be pretty heavy. IMO, in the event of a crash, it will not save the airframe, and is difficult to repair. From posts I have read on the TF Spit, weight is not our friend, so I intend to use the following old trick:

I use clear butyrate dope and silkspan, filled and sanded with a dope/talcum powder sanding sealer and primer/sand to the smoothness desired.....

Materials (LHS should have all but talcum powder - unless you have a "different" LHS ): Medium weight silkspan, clear butyrate dope (2 qts should cover the Spit, may take another pint), dope thinner (1-2 qts), 1 bottle talcum powder (scent at your discretion ), large 2 inch brush, tack rag, sanding primer (spray can or airbrush), wet/dry sandpaper 240, 360, 400, (and 600 - 1200 if you're a masochist! )

Preparation: After balsa surface dings are filled and sanded smooth, brush components with two coats of clear dope - about an hour (dope dries FAST, and the balsa will suck it in like a sponge) When dry, lightly sand balsa fuzz off with 240 grit paper. Remove dust with barely damp rag.

Covering: Cut silkspan piece of a convenient size* - can do an entire .40 - .60 wing panel in one piece with a little practice - dip in water, lay on towel to absorb excess water, apply dope to the area to be covered with a large brush, lay damp (not dripping) silkspan on the model (If I think the silkspan is too wet, I'll lay another towel over the wet silkspan and press excess water out. The silkspan should be just damp to conform to the surface, definitely not wet), brush another coat of clear through the silkspan to attach it to the balsa. If the piece doesn't go on right, just remove it, reposition it, or trash it and cut another... Repeat till all components are covered - on the Spit, I expect covering to take about four hours. It goes pretty quickly once you get a rhythm going Note - when dry, any excess silkspan hanging over edges can be either cut or sanded off easily, and the next coat of dope will lay the edges down nicely

*I usually precut all the silkspan panels for the component I'm covering, dampen and apply, then set component aside and cut next set.

Filling: When the model is covered and silkspan is "overnight" dry, brush on a couple of coats of clear dope, sand lightly with 240 grit paper, then thoroughly mix about 25% talcum powder in a jar with clear dope, brush and sand till the silkspan weave is filled (3 - 5 coats), stirring up the talcum powder regularly. I keep the talcum/liquid percentage about 25%, but progressively thin the dope as more coats are applied, with the last coat being about 50/50 dope and thinner... Filling time depends on drying - may take a while in the winter... I would plan two building sessions of 3 - 4 hours

Finishing: When the silkspan weave is filled, sand with 360 grit and use a tack rag to remove all dust. Spray on two coats of sanding primer (spray can or airbrush) and dry or wet sand and reprime and sand to the finish you want. In a fit of passion a while back, I ended up wet sanding the primer with progressively finer paper, finishing with 600 grit... talk about smooootooooth Time depends on finish you want... I'm planning four hours, then another four or six for the camo scheme...

HTH

Jim