Hi Alex

Just to share with you my little experience.
On my wooden fuse (similar volume as your own), before putting glasscloth I put dope on balsa. Then I put 25 g glasscloth with resin. Weight with resin after sanding is about 100 g.
But to get good finishing it's need to put primer. So primer is a litlle heavy 60 g. Paint is 40 g and clear coat is 40 g. 240 g total weight of finishing.
I think to get lighter is to replace glasscloth and resin by "japan paper" with dope. It's less resistant but you 'll have no problem with electric motor because less vibrations than thermic motor.
In this link see pages 25 to 27, finishing with silk, talc and dope (very long to do) : http://translate.google.com/translate?u=http%3A%2F%2Ff3a.sakura.ne.jp%2Fradioc ontroll%2Fspecial%2Fmake%2Faddction%2Faddction_01. html&langpair=ja|en&hl=en&ie=UTF-8
Claude