808FC on G3 is about £1300 + whatever RalTech wheel covers cost = a more serviceable wheel but heavier and I have no idea about the aeros?
If you're going with RalTech, you might as well build a good strong cheap rim and let the covers handle the air, there's not much point having a £700 rim under cover unless you're going to be uncovering it for IM 'no discs' races. My first choice rim to go undercover would be a Mavic XM819, but you'll probably want something with a brake track :-)
That's my plan. I have a mavic kysrium (super stiff but terrible aero's) that is fully covered with a raltech. Aluminium braking surface, reasonably light, cheap and easily repairable. Somethung wider would be good, but this will do for now.
If you're going with RalTech, you might as well build a good strong cheap rim and let the covers handle the air, there's not much point having a £700 rim under cover unless you're going to be uncovering it for IM 'no discs' races. My first choice rim to go undercover would be a Mavic XM819, but you'll probably want something with a brake track :-)