I've been having the same problem with my setup. After confirming the resistance was correct at the boards, I assumed it was some old SCR's. However, when I replaced a few of them I still had flicker. Testing today, it looks like I need an additional 470 ohms (tried 470 and 1k, 1k did not work) at the bulb. I think I have about 6-10 bulbs that flicker, some go in and out. My question is would a 270-300 ohm SIP work ok in the boards if I replaced the 1k ones? Or would heat/current be a concern here? For some reason my unhealthy desire to keep my crappy classic stern bulb arrays looking "clean" is trying to convince me not to just solder in the stupid 470 ohm resistors and be done with it... And when someone tells me to stop being foolish, presumably a 1/4 W 470 will be fine right?

Thanks for the info. Confirmed my thought that it would be too much current for the SIP, I will plan on soldering a few resistors at the lamp.

I don't in any way want to give the impression that I'm not happy with my purchase of these adapters. I think they work great, and would buy them again for sure even with the extra soldering on a few sockets. Soldering 10 or so sockets beats the 60 or so I would have had to do otherwise. They give a very clean look and are easily removed to make it "stock" if that's what is desired.