Ionly go 1/8 and I also use a cut off wheel and open up the clunk slit more and cut in another one, an X . My LHS now carries the fuel line like the stuff that comes with the new tanks, very flexable instead of me rebuilding tanks with standard fuel line. I'm using Tygon in my gassers and have to reline every year or it gets too stiff to move around. Iplan on going to the lawn mower shop and buying some of the line they use in brush cutters that stays limp over time. None of my LHS carry it, Ikeep hearing that line, we will order some but never see any.
Ithink this year I will retank with the bladder type of tanks in my glow planes. Bit more work fueling but it may be worth it in the long run. Ihave used them for racing and they work pretty well, no foaming or bubbles, you just need to fill them then remove the air out of the bladder, a bit more extra work.