I've thought about downtube, but they are hard to come by second hand here in the UK. I will be back in states for a few weeks in August though... Food for thought anyway.
I'm just wondering if the frames are OK on cheapy folders (like the citizens) and the components are suspect, or if the whole package is best avoided. Weight isn't really an issue for this bike, but it needs to be reasonable reliable without a ton of messing around.
I almost have a complete bike, minus a frame & fork, so what I'm really looking for is least expensive frame option of reasonable quality. The bike's only likely to be used for short weekend rides on MUP's and maybe by me if the Swift is out of commission & I need to use a folder.
my guess is that you'll be OK with a cheap frame. Generally speaking the bikes are cheap because of crap components. Sure, the frames aren't super high quality, but I'd be willing to bet that they're good enough for your needs.
Maybe a Mission Space Genie will work for you... I'm sure you can find a used one cheap in the UK.