I would have probably taken some sandpaper and roughed up the finish a bit over doing the channel locks thing. That plus carbon paste or such.

Worst case scenario is beer can shim but a well made product shouldn't need it.

I have a silver innicycle headset on my trek. I've got a power meter on the bike and have hit over 1300W on a sprint with the bike (hit almost 1450 on a different bike). The handlebars didn't move. I had to work up the guts to sprint that hard because I didn't trust things right after install and think it's generally a good idea to feel things out right after assembly. No issues. I'm running a cheap oem cannondale stem I bought on ebay for like 25 bucks.