some guys like flying bricks - scalelike they say--
an old rule of thumb is one lb =100 sq inches wing.
that is pretty good for planes in the 6-10 lb area-
as you get smaller - say 400 squares - halve that rule if possible
once you get to the 300 " electrics - halve it again .
Those numbers are hard to hit on most of the kits available - but most of em never get built anyway.
My 300 sq in Taylor Cub weighs 10 ounces - and flying weight will be one lb.- strange as it seems -it is on the heavy side----