I have my first three line fuel system going in a Carl Goldberg Ultimate biplane. The engine exits the cowl on the left when facing the front of the plane.

I've never mounted a fuel dot and before drilling a hole on the right front of the cowl where it seems most convenient, I thought I'd ask, are there any rules or guidelines or tips on where to mount the fuel dot for easy, convenient, clean fuel filling? Should I keep the fuel line away from anything under the cowl or doesn't it really matter where I put the dot? I can't imagine it'd make any difference but thought I'd ask first, drill second, just in case.

I mount mine through the fuse side, never the fiberglass cowl. If I decide to move it some day it's easier to fill a hole in the wood instead of the fiberglass or plastic. I have also had the cowls crack where the dot goes. I like to glue in a piece of hard wood on the inside of the area the dot will go so I'm not compressing balsa wood. I also fuel proof the heck out of the area.

Ditto.

Balsa is MUCH easier to repair or fix.

I have mounted DOTS in cowls when there was no other choice, and use the technique of first applying CA on the cowl to harden the entire area.

Then after a light sanding I EPOXY a hardwood backplate where the DOT goes, and finally a large washer behind the DOT to spread out the stress.

This has worked fine, but I avoid doing this whenever I can.

What they said. Mount them where you have balsa, or even better add a thin plywood backing plate. I mount Sullivan fuelers behind the cowls - where there is just a 1/8" hole needed with no external parts. Dots (and switches) I mount on the fuselage behind the cowl.

I like mounting it on the fuse too...make sure you mount it higher than the tank, or you will get fuel all over your hands and model every time you fuel and defuel(sp)

fuse is easier....but as an aside, we have mounted them in the cowl many times, but you would need to epoxy in some light ply behind the cowl to reinforce it......