A coworker of mine started his own business, Hackers Paradise, and he specializes in lowering cars and trucks. He has lowered a bunch of non-mainstream cars by stepping the OEM control arms.
If drop spindles are available he typically uses them, they are the better option.
Don't get me wrong, there is nothing wrong with homemade... as long as it's a good design and well implemented.
As for inspection of the modifciations, might I suggest you go to a local welding supply shop and ask for dye check materials. You'll need a spray can of cleaner, a can of penetrant and a can of developer. It's easy to use and it's great at detecting cracks. Here's a video https://www.youtube.com/watch?v=QpU5JyhNVgQ