Is the DUI harness a good choice, or are you mostly paying for the name? I have a perfectly good weight belt that I got before I bought my HP100 and don't use. Right now I use no ditchable weight though I'm not opposed to the idea.
As far as buy vs. rent.... the lake where I'll do my weight checking and training has a guy renting weights. However, I'd prefer to ballpark it myself and buy what I think will be enough, and give my weight system a dry run before even driving out to the lake. That is 75% convenience, 20% that the educational exercise is more effective with a real-world test at the end, and 5% that I just don't like renting stuff if I have a choice.
Again, thanks for the feedback. Much appreciated.