Booting these embedded systems isn't like booting an SSD on a regular x86 Machine. There are offsets and sizes to be observed.
I'll try to search it down tomorrow, but I wonder if mounting another partition during boot, but after the kernel loads might not be more effective? This is relatively easy to accomplish, but I don't know what software you're trying to include so I can't say for sure.
I had hoped that, since there's a settable variable in a script that specifies the size, that it would figure that out for me. The only constraint that I saw was 4k alignment, which shouldn't be an issue, since I just tried doubling the size.
Do you have the required bootloader image available?
If you don't change the size does it make a bootable card?
I did not try making a bootable image without modifications. I suspect that might be "broken" as well, since the contents of the image did not look like a bootable image.
Maybe I should have just asked if anyone knows the process for making a bootable sdcard. I suppose I could try doing it manually by copying a known good sdcard and resize/copy the partitions. That might work unless uboot is storing absolute locations, but I doubt it's doing that.
As for the software that I want to install. The partitions are only 90MB, so adding just about anything to the build will exceed that. Maybe the sdcard image was originally intended to fit on a 512MB card, but that doesn't seem necessary these days, and it makes life difficult to try things out.
Specifically what' I'm trying to install is gstreamer-1.0, which there is a recipe for, and it builds with minimal modifications, but doesn't fit. The version of gstreamer-0.10 that is installed doesn't have h264 UVC webcam support, and I'm pretty sure both versions will work side-by-side, so adding it shouldn't be an issue.