: How much filling is really necessary after sanding?

: I've sanded to what I think is smooth and fair but there are still a couple
: of 6" gaps about the thickness of a business card but I'm frightened
: to fill & sand because I think I've sanded those areas more than
: enough & I don't want to risk sanding through!!!!

: What are the implications of glassing and epoxying over such gaps?

The gaps should be sealed. If not, you most likely will end up with voids under the glass. These will appear as white looking areas and you will spend more time messing around with fixing this than if you filled the area to begin with.

I strongly 2nd Joe's advice

Tom