welding holes shut on fender - help!

[steverino66]

Thought about posting in body area, but I'll try you guys:
I'm preparing to plug front fender holes where emblem was removed (2 - maybe 1/8" holes); using Lincoln hd3200 welder with 75 argon/25 CO2 gas, .023 wire - new gas nozzle and tip.
I watched the Lincoln video, read the manual, re-checked all settings per chart on welder. This is my first gas welding attempt, I've successfully welded a couple of heavier pieces with fluxcore.
I practiced all weekend on a piece of 20-gauge scrap, drilling and plugging holes with a piece of copper held in back of opening - mixed results, a couple of lucky accidents but nothing consistent after about 25-30 holes of practice. Mostly ugly little molten piles, got blow-thru on higher voltage settings.
Any suggestions very much welcome and appreciated.
I'm not welding fenders until I figure this out. Rocker panels project is in my near future also.