Re: Need a new deck fill hole
Yeah, that will cut the hole you need but will probably be junk after one cut in fiberglass. You would be better off with one like in the attached picture. These are bi-metal and will last so you can use it again if you want. Cost more money though.
As far as using 90 deg elbows, it won't work unless you want to spend an hour at the gas pump to fill it. You need a pretty straight shot into the tank fill neck.