Well for those who are interested, I went ahead and bought 20 42-SMD warm white LED's from LEDKINGDOM-US on eBay. It was about $30 with shipping (to Canada).
My findings:
1) all bulbs worked and fit fine (they were about the same size as the original 921's in the trailer
2) they are quite a bit cooler than the Incandescent bulbs (but still do heat up though)
3) the Warm White is still fairly white, compared to the originals but not as white as I was expecting
4) the brightness surprised me the most (after reading everything I should not have been too surprised though). I actually considered getting smaller than 42-SMD thinking they may be too bright and am glad I did not. They are noticeably dimmer than the originals, but I found that I have so many lights in the trailer we rarely ever had more than one light on at a time. I downloaded a Lux meter app for my phone to get a rough estimate of brightness. The numbers surprised me the most. The difference, at daytime, with blinds drawn, measured at 1' distance was about 10x. See pics (original bulb on left):



If I was to rate how this experiment turned out I would give it about a 6-7 out of 10. I think it is still a good thing, as I cut my battery use way down, even if I have to run a couple of lights instead of just 1, and for the cost of a couple of bulbs at the more reputable vendors it was still worth doing.
I will retest late tonight to see how I like them.