To get certified for just about any type of welding requires that you do full penetration butt welds from one side. You have to be careful because too little or too much penetration will fail. You want the penetration to be about the same height as the cap on the outside, roughly the thickness of a dime. Pipe is the most common thing welded from only one side and there's no way to add braces. You don't have to be a certified welder in order to want the maximum strength weld when only one side is accessible. A test plate isn't a test plate until you test it. Welding 2 plates together and declaring they hold or are strong is no different than if you stuck them together with JB weld. Put some load on them to see if they are as strong as the base metal. Ultimately that is what you want to accomplish when you weld something together.
If you're welding say 3/8" plate with a machine only rated to weld 3/16", it's going to be a cold weld due to lower amps and not enough heat input into the thicker base metal. You might need lower amps for the root pass but then you want more amps for the "hot" pass and subsequent passes. A 220 machine would be able to put more heat into the weld. If you were welding the pieces with solid wire MIG, you wouldn't really need to stop for more than a couple seconds when ending one pass and starting the next. Even if you were stick welding or using flux-core, it would only cool for a few seconds while you cleaned the slag. When welding thick steel, they don't just fill it in with one big pass. They use several smaller passes and in a lot of cases it's faster to do more small passes instead of one big slow pass. Preheat is often used as well and on critical welds, the weld procedure will even specify the interpass temperature. Sometimes you don't want too much heat in the base metal and have to let it cool a bit before the next pass. Look at the spec. sheets for Lincoln NR 211 flux-core wire. It requires something like 22 passes on 3/4" plate to meet the AWS requirements.
I don't care if it's stick, MIG, TIG or A/O welding, If you're a beginner you need start on simple projects until you know what to look for and can produce quality welds. MIG is famous for having what looks like a perfect weld when in fact it is cold lapped or has other hidden flaws. That's where doing some practice test plates helps a lot.
If you're welding say 3/8" plate with a machine only rated to weld 3/16", it's going to be a cold weld due to lower amps and not enough heat input into the thicker base metal. You might need lower amps for the root pass but then you want more amps for the "hot" pass and subsequent passes. A 220 machine would be able to put more heat into the weld. If you were welding the pieces with solid wire MIG, you wouldn't really need to stop for more than a couple seconds when ending one pass and starting the next. Even if you were stick welding or using flux-core, it would only cool for a few seconds while you cleaned the slag. When welding thick steel, they don't just fill it in with one big pass. They use several smaller passes and in a lot of cases it's faster to do more small passes instead of one big slow pass. Preheat is often used as well and on critical welds, the weld procedure will even specify the interpass temperature. Sometimes you don't want too much heat in the base metal and have to let it cool a bit before the next pass. Look at the spec. sheets for Lincoln NR 211 flux-core wire. It requires something like 22 passes on 3/4" plate to meet the AWS requirements.
I don't care if it's stick, MIG, TIG or A/O welding, If you're a beginner you need start on simple projects until you know what to look for and can produce quality welds. MIG is famous for having what looks like a perfect weld when in fact it is cold lapped or has other hidden flaws. That's where doing some practice test plates helps a lot.
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. I would weld another at 60-degree example if nobody else is willing. But after the weather cools down, and... if it seems like the forum needs more action 
